I dunno the the 8 mans can kill pretty fast(will be geared compared to the zergs) and its the same amount per kill as a zerg, but without having to try to tap every mob or compete with the AE groups. The one 50s I saw last night were just 8 manning , they didn't go near the zergs.
I'd the say some of the main postives from zergs was gear didnt matter, most people were in level 1-15 gear(@35+) including weapons, levels didn't matter and maybe kill speed(if you can get a tap on every mob).
I loved 2 group group BGs, but when it got into 50+ ppl, it was just no more fun. Don't mind going back to just 8 man groups and it will still be relatively fast.