The search for the next car has begun so I tried out the aforementioned cars, both for a week and about a week apart from each other. I should mention that I currently drive an IS300h and have previously had a CT so I can do I decent comparison. If you are looking at something along the same lines just now this may help although it is all subjective and your opinion will undoubtably differ!
The BMW is obviously a plug in Hybrid which provides for about 20 miles of electric power. The GS isn't and doesn't although you can probably get a mile out of it given the right conditions, maybe more. Both cars are targetting the same segment and with the BMW's green credentials, is quite a close competitor. On paper, the GS, especially in Exec spec, is a lot lot cheaper. The current GS Exec is around the 36k mark. The BMW starts around 44k but the £2500 government grant applies so that brings things down a bit. The car I was provided with was the M-Sport with a variety of technical upgrades which brought the cost of the vehicle to an eye watering 55k. This makes direct spec comparison difficult but I think it is fair to say that, generally, feature for feature, the Lexus is better overall value.
Engine/Performance and Plugging In
First things first. The BMW is faster than the Lexus, much faster. It also sounds half decent as well which is nice although I have to say I felt the GS did a great job at dealing with engine noise, especially compared to the IS. In normal use when not pushing it or accelerating hard then both cars are as quiet as you would expect and any noise from the engines is kept to a minimum. The GS seems slightly keener to maintain the battery power compared to the IS although my understanding is that the engines and hybrid systems between the two models is identical so that could just be my perception. Obviously the main benefit of the Lexus in this context is that you don't have to plug it in. The plugging in of the BMW is really essential if you want to realise the benefits of the car and I will talk about this below.
In essence, both cars are fast enough but if overall performance from standstill is important to you, you should opt for the BMW. In normal use, there isn't really that much difference - the GS in sport mode seemed perky enough.
The GS is a known quantity - I didn't do a brim to brim measurement but the on board mpg said I got just under 50mpg in total with a whole variety of different driving. Take up to 5 mpg off for over enthusiastic measuring and I don't think you will be far off the reality. I found that okay and comparable with my IS which has done just over 48 mpg over 2.5 years. The BMW was much more variable. The truth is that, if you want to get the best mpg figures you will need to plug it in at every opportunity. I managed a commute home from work which was 50 miles and mostly motorway, achieving 83 mpg. Other trips really depended on what mode it was in and how much battery is left. I would estimate that if you have a full battery then you will get good returns depending on where you are going. The issue is that the battery is small and will be depleted after most journeys. There are ways to stop this from happening which I will touch on later but if you can ensure a full battery you will be a happy camper. If the battery is depleted, it will run in a similar way to a Lexus, charging and using a small percentage of the much larger (compared to the GS) battery in an automatic hybrid mode. Fuel returns, I would estimate, are slightly below the GS when running like this but you do have a bit of extra power as compensation.
Learning to keep plugging it in was a bit of a culture change and I hadn't anticipated what a pain it would be. I don't have a drive and so ended up running an extension cable out to the car - obviously if you have your own off road parking then this isn't an issue. At work, no charger again although I did manage to get to plug it in overnight there a couple of times. The availability of chargers is key though to making the plug in work in a cost effective way. You can also force the battery to charge from the engine. Driving up the M6 for an hour fully charged the battery doing this but at the expense of a fuel economy running in the mid 30s or less. Whether this is worth doing is debatable but you may want to rely on the battery only for some reason. It is good that the option is there and with experimentation you could change the settings to maintain the battery at a certain percentage (other than 100%) to strike a balance. I wasn't able to use on-street/public charging points only having the car for a few days but it surprised me just how much you need to plug the car in to ensure it is ready. I am sure you would get used to this over time.
Handling and Gearbox
This was surprising. For the most part, the 8 speed auto in the BMW was generally very good but not all the time. There was an annoying lurch between 1st and 2nd which wasn't there all the time but that made if even more noticable when it happened. It was also hesitant and, to be honest, inconsistent with the power delivery when accelerating on occasion. Pulling out of a junction was tricky at times since it was like hitting a powerband - nothing at all and then BOOM! The much derided by the motoring press e-CVT in the GS, by comparison, was predictable (boring?) and smooth. I didn't have any issues with it and despite the noise and the slow response this transmission does have, it felt much better suited to this kind of car.
I thought the handling would be a clear win for the BMW. Not so. At very slow speeds I found it has overly light steering and zero feedback. When picking up the pace or on the motorway, it did improve but the slow speed handling combined with the uneven power delivery did not inspire confidence at times. The GS was sure footed and, I though, was really quite sharp and precise. Overall I preferred the feel of driving the Lexus (but maybe that is because that is what I am used to).
Special mention should be made of the brakes - or more precisely the regeneration of energy. The Lexus felt like every other Lexus - very gentle regeneration if coasting and only really coming in when braking. The BMW sometimes felt like that and also sometimes felt like a proper EV with very aggressive regeneration that only seemed to cover certain speeds. It was a very inconsistent experience overall and I wonder if I had missed some settings or didn't understand quite what it was doing. Even so, despite the system beings fairly capable at recovering energy I really didn't like how the whole experience lacked consistency.
My car did not have the safety equipment fitted such as radar cruise control which comes as standard on the GS. I would have specified it and it worked really well on the GS. Overall though, the BMW was way ahead on this front. The screens, full digital dash, presentation, ability to set a time and have the car warmed up and ready to go, the key that was like a phone with a touch screen and the really nice interior lighting, all better than the Lexus. Having said that though - most of it you could do without. The HUD and general infotainment stood out. The rest like the fancy key and gesture control, although worked as advertised, felt like party tricks you show everyone when you first get the car but add little and cost a lot. Still, Lexus could really do with reviewing the graphics and features of the in-car technology. It is entirely functional but doesn't feel as special as it does in the BMW.
The BMW was fitted with a £900 Harman Kardon audio system and I was disappointed despite fiddling with it - it was clear but just lacked a bit of sparkle and punch. The base 12 speaker system in the GS sounded better to my ears (in surround mode which normally makes things sound a bit worse). I would like to try the ML system for comparison at some point. A Bowers and Wilkins system is available for the BMW but at £3500 I don't see that as a good buy! My children enjoyed changing the volume by making circles with their fingers in the air but, as you will imagine, that got old fairly quickly.
The parking system incorporating auto parking and a 360 camera system worked very well and was super flash as the camera zoomed over the car (or you could get a remote view of the vehicle wherever it was parked and wherever you were via the app) to show the best view. Auto parking was fine but it didn't always pick the right parking space or seemed to make too many turns. I have always found the Lexus system with the park assist to work just fine - especially for parallel parking. They really should upgrade to a 360 version on all models or at least put a high definition camera there.
Bear in mind though you could get a fully specced Premier for MUCH less than a comparable 530e so overall costs favour the Lexus.
The big issue I had with the GS was the seat height. It didn't go low enough and I always felt too high in the car. The seats also felt quite a bit harder than the IS. The car was new though so that may have been the reason. Also the headrest came forward too much and only seemed to extent a little bit. I wasn't uncomfortable at all but I couldn't get it quite right. This height didn't help in the corners and the fairly wide seat meant I didn't feel all that supported (the IS seats are narrower and suit me despite the fact that are only 6 way adjustable). I would expect the 18 way seats in the Premier would solve this. The BMW came with the comfort seat option (no massage or ventilation though) and they were designed for someone a bit... wider than me. The bolsters were adjustable though and I would expect the level of adjustment would match the premier grade of the GS. The steering wheel didn't come quite as forward as I would like in the BMW but I was able to be comfortable in both cars and do long journeys without any issues.
To me that really means fuel capacity and luggage capacity. The boot space was only 411 litres (from memory) in the 530e. The shape of the boot was fine though and I didn't have any issues getting all my things in there. The GS has a totally different shape and 450 litres which I actually prefer - open the boot and it is all there rather than have to slide things for miles into the car. The BMW did have a powered boot which allowed you to lock the car and close the boot at the same time. I found that really useful. The GS actually had an undocumented (in the sales brochure) soft close feature but the GS and especially the IS really need to have damped hinges to stop it bouncing open. Auto closing is an option on the GS too to be fair.
I won't really go into this as it is too subjective. Overall you will not be surprised by the design of either. I liked elements of both although the GS was more distinctive at the front, the BMW was neater at the back.
If you have made it this far, well done. Fire any specific questions my way if you are considering the 530 or GS and can't get your hands on one. Which am I going to choose? Will it be either of these? I will say that both are very very good cars with elements that delight and annoy like any car. In the end the choice is yours but I will mention that while the BMW is more expensive to buy outright, depending on how you finance your cars, it may be the cheapest to lease as well has have a lower tax burden which is only 9% this year so could be the cheapest one to own.