So I had to make the same decision about a 128i over a 135i. I really love the power of the 135i, it's totally addictive. But it is quite a bit more money, and I almost always buy only a minimalist car. I decided to go for a 128i after I was able to test drive a manual 128i with only the cold weather package, and no sport package. The car was great (well at least that was my first impression.)
Manual compared to Auto 128i was the clincher for me. The manual on the 128i is much more responsive than the auto. Much bigger difference than the 135i.
I was also able to get it cheap and in 2009, the car had better options than now (i.e. sunroof, and 10 speaker audio.
After a year, I decided to start prepping the car for some weekend AutoX. Tires were first (hankook V12), and this opened the flood gates. Well the tire were such and improvement that the suspension float really stood out. So I spend $2700 on BMW performance suspension + springs. Awesome!! (Do this when you order the car, it is way cheaper)
So $30.5K car + $1500 Tires (winter wheel + tire and Summer Tires) +$2700 suspension = Killer 128i for less that 135i.
I was recently in a 135i again. I think compared to my car the stock 135i is not as much fun. More powerful, yes.
I'm really happy with the 128i plan on keeping it to 85K-100K mi. BUT
I think my next car I'm going to order is a 135i, w/performance suspension and do either PCD or ED......
Your will be happy either way, but in the end you will always be planning to get a 135i next time
