I didn't say the GS has less wind noise that the 5 but less road noise. I agree the GS and 7 are completely different cars - a comparison between the GS and 5 is fairer so here goes (I owned a 2000W 528 Sport for 12 months and my GS is 2000X):
Road noise : GS wins - the firmer suspension of the 5 lets in more road noise. I don't think it's tyres as my GS has 235/45 all round (Goodyear GSD3) and the 5 had 235/45 front with 255/40 rear (also Goodyear GSD3).
Wind noise : 5 wins - Anything over 65-75 in the GS creates a very irritating wind noise around the front and driver side windows. Seems this is not a problem with the GS, just the way it is. The 5 had better isolation from wind noise (but not as good as the 2000X E class I had before that).
Ride : 5 wins - As mentioned by NickF, the GS just can't manage on anything other than brand new smooth roads - twitches around continuously on less than perfect surfaces and lets you know about all the imperfections in the road. The 5 rode over bad surfaces very well although you could really feel speed bumps with it's stiff suspension. ColinBarber asked which Lexus I had - I believe it is the 2001 model year as I have the new style rear lights and DVD satnav and if this is an improvement over the first version of the GS II then all the more shocking that Lexus could not make this any better. Surely the LS doesn't behave like this?
Handling : 5 wins (just). Both cars feel pretty precise in handling and agility, but as the 5 rides better over imperfections, one feels more secure in rapid changes of direction in this car over the GS.
Comfort : GS wins (just). The GS seats feel more cossetting - very luxurious. The 5 (I had sport seats in mine) feel firmer at first but are comfortable for long journeys. However, I prefer the GS seats. The climate control in both cars seems pretty good to me, although I think the GS has better air distribution (like the little channel which blows under the steering wheel right between your legs )
ICE : GS wins. The standard stereo on the GS is unbelievable. The 5 has a very ordinary amp and with the lack of a standard sub as the GS has, lacks any real impact when the volume is pumped up. The Mark Levinson equipped GS cars must be out of this world.
Interior : 5 wins. The GS looks a bit ordinary on the inside - except for the binnacles that the instruments sit in, the rest of the dash could be from any Toyota, and it doesn't have flowing lines as in the 5. The 5's dash is very ergonomic - I really like the way it flows and the slight angling of the centre console towards the driver.
Exterior Looks : 5 wins (just). I like the 5 series (E39) looks - a classic shape I think, but when fitted with the sport kit, looks a lot like an M5 so even better looking. But the GS is very nice - even the GS Mark I still looks good. A GS in sport trim looks even nicer that a GS SE, but still not quite as cool as a 5 series with full sport kit.
Running costs : 5 wins. I've not had to service the Lexus yet, but from what I've read it appears servicing costs are not that different - but the GS needs servicing every 10k whereas my 528 was averaging 15k service intervals. So even if the 5 cost 50% more that the GS to service, it would work out the same over a long time. The fuel consumption in the 5 was better on the motorway that the GS (average 30mpg at 90mph in the 5 but only about 26-27 in the GS).
I could go on, but possibly at the risk of boring everyone to death (if not already done!). But overall, I think I still stand by my opinion that while the GS is a decent car, it's not as good as a 5 series. From what I recall, I believe the 5 series took WhatCar executive car of the year for 5 or 6 years consecutively, and I think there is much merit in this fact.