Well, after having a 2001 BMW M5 as my daily driver until last month...I do have to say it was quite an experience.
Simply put, the BMW M5 is THE performance saloon of all time, in every respect. The Lexus doesn't even come within twenty feet of kicking its tyres.
...for example...try cornering hard on a Lexus, and you'll be praying to God that you're never foolish enough to test it again- dynamically, the Lexus sucks, build quality and finish can't match the Beemer, nor engineering/durability as pointed out...then of course...we have that other little thing...IMAGE!
The only reason I sold my M5 is to get a new 5-series: it's a 545i auto that arrived last week. Very nice indeed.