Echoing what Mr. Tanner has said, GBBR/GBBSMG for indoors is tits. You dont go through as many rounds playing indoors and the realism and badassery of a bang stick can't be beat in close quarters.
AEGs are best for mid-long range engagements as they have more consistency in all weather conditions and have a larger magazine capacity. To get through bush you gotta put some volume down range. As well, if you are like me and like to be a stalker in the bushes an AEG is better simply for noise factor, or rather the lack-thereof.
Ultimately it boils down to what kinda of environment you intend on playing in most often; I would go from there. I have 2 GBBRs and 1 AEG, but for variable-range-all-weather-bitch-blasting my super-tuned AEG is the go-to simply because it never goes down.
Guardians of Asgaard
NO EGO, ONLY HARD WORK
Primary - Z-Custom VFC ZTW
Secondary - KWA ATP