It depends on the situation really. For local events I prefer to use a sidearm, but I have been to several events that require an AEG and sidearm for snipers. The cqb m4 is a good choice, it leaves you with the ability to share mags if the need comes up.
Pistol all the way. Tried an Mp5, and it was just a paint to carry. Especially when playing a normal rec game. If it was a long three day thing, I might think about some more firepower, but a pistol and some spare mags will suffice for most games.
I used to carry my 5-7 but i have a mag leak issue at the moment. I set up my BLS belt with a weapons catch and plan to sling my M4inside my ghillie jacket when using that or just on the outside of everything when not.