If you're worried about ride comfort, I just saw a Black E90 M3 with 19" LM's and it looked SICK. I was surprised because the 20's definitely look better in the pics, but this looked really good. It was lowered.
Let me get this straight... You are swapping out parts designed by some of the top engineers in the world because some guys sponsored by a company told you it's "better??" But when you ask the same guy about tracking, "oh no, I have a kid now" or "I just detailed my car." or "i just got new tires."