didn't read this whole thread, but here's my .02
performance wise, the 335i wins.
everything else wise, the is350 wins.
the 335i is a great platform, or so it seems, if you want a classy, sporty vehicle with good performance and is easily upgradeable.. for only 1,200-1,500 you can get up to 350 rwhp and over 400 rwtq.. thats not bad at all. one thing i hate about the 335i is the terrible placement of the cupholders... i done broke my knee on them and broke the passenger one on my friends car...
i ofcourse love the IS350... but i hate that its not offered in a manual and the performance side of the aftermarket world has yet to really offer anything really substantial.
price is another issue.. i hear that people are paying over 60K in california for the 335i while the IS350 is now being heavily discounted.
reliability... bar none... lexus is the shit!
service... bmw can't touch lexus service.. they dont even come close.