CO has an airport club at FLL, if that makes any difference.
If you travel mostly in North America, I would recommend CO because of their unlimited upgrade policy. AA's MRTC is really nice, but if you can sit on first, why cares?
I believe AA serves the infamous cold "bistro bag" on this short route while CO will get you a hot sandwich if you stuck in coach.
My recommendation is to find a way to get an elite comp from CO.