Hi,
I have both an IS 250 AWD ' 08 and a BMW 335 XI ' 08. In my opinion, they are absoutely different cars, and if you are thinking of one over an other it is not a fair compairson. I honestly am suprised how different the two cars are. Here are my compairsons:
Interior
IS - Really nice leather, the black interior is very rich looking and feels so smooth. The BMW 335 interior leather is hard, and the head rests are very uncomfortable, but the seats are very supportive. The IS is a little smaller in the back seat while the BMW has a decent back seat. The NAV system on the IS is a disappointment. The positioning is very bad, if you have the sun roof open the sun blocks out the screen, there is no interface for the IPOD where you can load your playlists on to the screen and control the IPOD, my IPHONE doesn't load the phone book, and the system doesn't let you control anything while you are driving unless you use the steering wheel controls. The Nav on the B is much more intuitive and easier to use. You can navigate on the fly as you are driving where in the IS you can't put in an address unless you are stopped. The I Drive is easier to use than the touch screen, because of the many options that you can control, that the IS only the dealer can set.
Styling
I think the IS has better styling and design inside and out.
Power,
The 335 Kicks the IS's A#$. The Twin Turbo of the 335 is really awesome, and the IS feels very underpowered. If Lexus would have put another 50 HP in the 250 it would be a great car. I always say put the 335 engine and the electronics in the IS and you would have the perfect car.
The 335 takes a lot more to drive than the IS. IS is very smooth and supple, while you have to work with the 335 but it is a lot of fun.
Finally attention,
Everyone says that they don't buy the cars for the attention but honestly we do like the looks... The IS garners many more looks from everyone, girls and guys alike. I am 30 and thought the 335 would get more attention but the IS really wins in the attention category. People who know what the 335 is and how fast it is look and like it, but the general public seem to like looking at the IS more.
I hope this helps, from someone who compairs every day which one to drive to work
Keith