For me I find the biggest limitation of a GBB on the field is the lack of ammo and gas and is weather dependent (at least in the spring and fall, not so much in summer). If you get a good gun like a TM Hi Capa 5.1 or P226, range is not that big an issue. I've played a few field games where my AEG goes down with only a pistol left and have not had any issues getting kills.
With a pistol though you just can't camp at the end of the field, you have to be aggressive. If you're a newbie at airsoft though it's not recommended though.