Personally, Looking at the S4 & Is350 side by side - Power is basically the same I believe the S4 puts out a bit more power. Obviously German engineering / japan made. My biggest factor came down to reliability & cost. And of course other stuff. I went with the Is350 because the S4 was like 15 k more

 

The IS does make decent power, but it's higher up in the RPMs, so you don't feel it when your just cruising around. The S4 feels like it has a lot more torque available at lower RPMs so when you're cruising around, it feel more punchy. And if you do happen to stomp on it, you'll take off like a rocket, no matter what RPM you're at. My 335i was the same way. Both these cars kill the IS on usable power.

However, the IS350 still has enough power to be fun and make a really great daily driver. IF the cars were the same price, I'd get the S4. But they're not the same price, and I couldn't justify the price of the S4.

I do find that the IS lacks a little "soul" for lack of a better term. It's so composed and refined that it doesn't have much personality compared to some other cars.

 

U basically said it. I test drove the 335i sport and yea it is very refined compared to the other makes/models. I do love lexus but I feel that they take alot from the rides