Velocity Arms has some pretty good clear guns (the new custom VA line) however once AV'ed the classifieds are your friend.
MP5 or M4 you can't go wrong however the M4 is probably more "versatile" in that you have a plethora of accessories and configurations (M16, M4, CQB, SPR, etc.).
In addition AK style guns aren't bad for starter guns either since they're pretty common and easy to find replacement parts for.
I would say if you played paintball before then go with the style of play you like however since you play "every style" I guess pick whichever you like more. The mechanics behind all airsoft guns are pretty much the same so one isn't really better than another, all you need to think is that it's basically all the same motor and piston between different brands with a different shell outside (this isn't *true* since you have different versions of gearboxes but it's easier to think of it this way).
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE