Imo only GBB guns that can be skirmished effectively are smgs and pistols... the GBBRs are better left for DMR roles or strictly milsim.... in skirmish, you have guys dumping BBs at you from AEGs, you will be severely outgunned and you'll find yourself reloading mags more than you are shooting.
If all you want to play is milsim, then have at it. Problem is, you are not of age, and most game organizers will not allow minors to participate in milsims... so we are back to skirmishing.
In the end, it's your own choice, but the safe play is to go with an AEG.
Also, I encourage you to try before you buy... like kalnaren said... bullpups aren't for everyone, but if you have no prior experience to go with, then bullpups can be for you since you start with a clean slate. lol.
I don't mind either, I've run with an m14, g36 and a p90. Only issue I run into is forgetting how long a traditional rifle is over a bullpup so I usually bump the front into things first few firefights in a game.