If youre torn between the 128i versus 135i, here is my opinion.
Over the years Ive most enjoyed driving smaller cars with sporty suspensions and revvy engines with well-mated manual transmissions--- Volkswagen Rabbit, Acura Integra, Toyota MR2.
Then in the early 90s I bought a Nissan 300ZX twin turbo.
I learned two things from that car.
One, a car that is overpowered for daily driving is not that much fun.
Two, turbo lag always feels unnatural.
The 128i is a fast car, more that powerful enough for fun street and mountain road driving, the gear ratios are fabulous and the throttle response is wonderful.
Unless 0-60 is your first priority the 128i is the better sports car.