More doesn't make it better.
Yeah, the best MP shooting experience I had were always 3v3, 4v4, 5v5, 6v6 matches, at best 8v8 but such player count is already hugely dependant on the map/game design, and BFBC2 with it's 12v12 being the absolute maximum I ever enjoyed, actually being one of the best MP experiences ever, top 5 easily, but that game was exception from the rule, and even DICE themselves have no idea how to recreate that experience. Bottomline is, the principal is extremely simple - you want to put more players on the map, you need to make bigger maps, and when you make bigger maps, there's more walking than actual shooting, and walking is not the reason I want to jump into MP shooters.