If you're buying diesel then don't buy Japanese, let alone Lexus. The best Jap diesels are the Honda lumps, and even they disappoint IMO. VAG diesels are the best in the world, bar none. Despite being tuned to within an inch of its life my old PD130 used to return over 50mpg and would happily spin the wheels in 3rd in the dry. The CR lumps in use now are more refined than the one I had. No faults over the two years I had it and I abused it like you wouldn't believe. On the move it was quiet and pulled like a steam train. The Toyota diesels are unbelievably noisy, inefficient and unpleasant in comparison. If you want a 'luxury' diesel then it has to be an Audi - they're prolific for a reason! The BMWs are refined but not particularly dieselly and under real conditions are (or certainly were when I drove such things) less efficient.
If you're going petrol then the IS250 is probably the best real-world car I've had the pleasure to drive. Mine returns 25-30mpg on my commute (5 mile round trip - it barely gets warm) and I have seen 44mpg on a longer run, though I was trying (but still exceeding the 70mph limit). It's quiet, smooth and is the only Japanese car I've ever driven with a decent automatic gearbox. I have utter faith in it and after 10k I'm still impressed (I fall out with cars within a month or so, normally). I wouldn't have a manual version, and seemingly neither would everyone else as Lexus ditched it. It really is a FAR better car in every respect barring economy - in that regard the difference is less than you'd think. It's probably fair to say if you can't afford the difference you probably can't afford a Lexus come service time anyway...
I'm sure the Lexus will be awful in winter, but it's on summer tyres so that's to be expected. We've got the missus' MX-5 if it gets really snowy and I need a manual gearbox to get going.
To tie this in to other comments, I'm also an advanced driver and a biker. Not sure how that's relevant to the IS220D though.