Thats a good question not easily answered. It really depends.

Worst case scenario is guild guilds split between the two, which given their crappy timing is a real possibility.

AoC will probably play/look smoother, and be a bit more polished overall given Funcom is experienced at MMOs and well funded this time around, but DFO is the game many of us are looking for regarding a next-gen UO/Shadowbane PvP warfare game.

Regardless of DFO, is AoC is polished, and out, a decent amount of ppl will have a hard time prying themselves away, yet quite a few of us will be playing DFO regardless, untill/unless it proves to be totally unplayable.

Only time will tell.