Of the three I would go with an S5.
The Supercharged engine is *extremely* flexible. The 335 is a beast no doubt but I see 3 series everywhere. I see far less A5s, let alone S5s. I prefer Audi's interior as well as MMI over iDrive 2.0. If you put a gun to my head and said pick a 3 series, the 335 would be it. Make mine white with red leather interior: a pretty rare combo.
Curious though: when you say space how much do you really want/need? The two coupes are not home haulers by any stretch and I would only put people I don't like that much in the back seats unless children.
- b