Slow - I don't look at either of these cars (the 128i or 135i) as 'race cars', if I wanted a race car I'd do what a buddy of mine has done and find an old Datsun 240Z and gut it and build it back up. I'm looking at the 1er because I want something small, relatively powerful, with OK mileage, that'll convey She Who Must Be Obeyed and myself on back roads in decent comfort and with sufficient verve.
I want to enjoy AZ Route 67, with it's synchronous switchbacks, as it wends its way to the North Rim of the Grand Canyon; I want to be able cover endless miles of Blue Highways in the high plains in a car whose seats don't envelop, but rather, support me; I want a car that won't feel 'constrained' as we trundle around a courthouse square looking for the local watering hole in a verdant Iowa town.
I'm not, however, looking for a car that will improve my sex life, win the Indy 500, reduce my cholesterol, or make me handsome. There's no chance I'd be able to win the Indy 500 even with the right car. As for the handsome part, see my previous response re Indy . . . ; -)
I had a chance, thanks to Bryan at Motivemag, to do a quick drive of the 135i. It told me that the car can be driven slowly w/o it feeling constrained. It also told me, that while the absolute cornering limits may not be the same as the Miata, it'll still get me through the twisties with a grin on my face. (Here's the thread with my babbling:
http://www.1addicts.com/forums/showt...ht=impressions )
I want the 135i over the 128i because of its 50-70 acceleration numbers. I spend a lot of time on two lane highways, prefer them, and the 50-70 times tell me how much exposure I have when passing other cars. The lower that number the safer I am. The other reason to go with the 135i in my case is because it'll spend time at altitude in the west. The turbocharged car will suffer less at altitude than the naturally aspirated 128i. Futher, the technology of the N54 engine fascinates me. 'Good dog food!', as a friend of mine says.
I looked at how I drive - where I drive - and who I travel with and after factoring all of that in I have found that the 135i will meet my needs. It's not the only car that'll do that, but it is the car that suits my needs with the fewest compromises.
Don't know if that helps, just my 2 cents.