Hey Rossifumi, no sweat, man! It's all good. I was really confused at first too, before getting my F34, since some catalogs have it using the same size wheels as the F30s. But yeah, they're bigger wheels for sure.
I would love to have 20" rims. And think would look better. Just too impractical where I live, unfortunately.
Edit to add:
Anecdotally, my buddy had 19" M5 reps on his E90. Looked great! but after a year, he could not wait to get back in 18" wheels… the harshness and the number of flats and blowouts he got from our roads just rendered 19" wheel impractical for him… Fast-forward to me, since I have a larger wheel diameter, I can afford to have 19" wheels and keep the same tire height as his 18" wheels on an E90. Any shorter on the tire height, I'm just looking for trouble in terms of pot holes, flats, and dented rims…
sad… but when I move to a city with better roads, I'll look at 20's. (FYI, my OEM staggered 18" 400M's are my winters, wearing Blizzaks LM-32's)