[bradleyland]

It's all about size and character. If you drove an E92 3-series coupe and an E82 1-series coupe, you probably already know the differences. My brother-in-law bought an E92 335i, so I've driven both a bit, and there are definite character differences. My 135i feels smaller and choppier, like Red Bread said. I think choppy is actually a really good description for the way the 135i drives. Some people might think that's an insult, but that's how I prefer it. When I drove my brother-in-law's 335i down the Blue Ridge Parkway, I could tell a distinct difference from my 135i. The larger car floats a bit more over uneven roads, where the 135i kind of hops over them. This can be good and bad. On a smoother road surface, it gives the 135i a tighter feeling, IMO. On bad roads, it can be unsettling.

Neither the 2-series or the 4-series has been driven by anyone outside of BMW, so we really can't say for sure if these comparisons will hold true for the new cars, but I would expect BMW will try to keep their characters distinguished, so it's reasonable to assume the differences will remain similar.