My 2 cents. Just got my first 4s 2 months ago (ys 63). Wow!!!ran right out of the box...have not had a problem with it yet.

Most of the guys at my field only do 2s and gas engines, only a handful of 4s, and only 1 other ys (he has several problems with it...I told him I would take it off his hands for free).

While I believe you pick a motor based on the application I will always consider buying 4s over 2s (except for speed planes).

Oh, did I mention, since I have the only good running ys at the field, I am the envy of many (they just cannot get over how quiet and powerful it is...).