XP for CV is depended on your team attack not your own, so if you want max your XP, You have to try make your team win. Your own attack is almost totally invalid. I noticed to, that you can get best credits when you have both type of attack (on planes and on ships). For now playing as FW is easiest. There is more FW than BW and best setup for counter FW is other FW. BW right now require more skill to avoid all those FT, smoke and then successfully bomb your target. Of course, you shouldn't take setup you don't like, if you don't want leave this game because of boring.
And Yes, there is a balance issue. Watch on test server threads on this forum. They try to do all type of setup comparable to others (FW shouldn't be best option at the end, but other setup should be as good as FW. We will see what happens).
Exp from all setup is equal when win and lose. So FW/BW/RW/Mixed gives you similar exp for win and for lose.