I haven't been playing a lot of 3's or 4's recently but usually when I do, I normally feel like I got outplayed when I lose. If one side is stronger, I couldn't tell you which.
Also, 3v3 and 4v4 are the same game only to people that don't play them much (or possibly don't play them well). The dynamics of 3v3 are different. I have friends who have been part of teams that were top 20 in 4v4 that won't play 3v3 because it is that different.
+1