Best thing would be to get out to an event or two in your area, see what people are running and what people are comfortable fixing/troubleshooting. all AEG's are basically the same internally, with specfic quirks depending on what you are working on.
the best advice is find a gun that you like the look and feel of, if you dont like it, you wont play with it. I am also sure it would be long before you start looking for a second gun.
Thundercactus makes some goodpoints also.