Primary: Classic Army SL-9 w/6 50-round magazines
Backup: Tokyo Marui MP5A4 w/13 magazines
After playing for several years, I can say that I'd take a backup AEG over a pistol anyday. A backup though is really only usable if you have the mags and kit for it.
A good quality primary that's properly maintained (or upgraded), with a couple of spare batteries is a much better idea than three less-than-acceptable quality guns.
"Someone in a Prius tried to race me at a stop sign the other day. I couldn't believe it. I had him for the first 100 feet or so but I can only walk so fast."