I think consistency and stamina are more important if you have one primary runner, and less so if you use two backs (like a pro set or wishbone style offense). With two runners, your guys shouldn't tire out as quickly sharing the rushing load, and if one of the two has a bad game, you aren't as likely to be sunk since there's another back to make up for it.

I don't recall Orlando Singh fumbling very often for me last year, and he only has 3 carrying. Maybe it was just luck, or maybe he fumbled more than I think and I didn't notice because none of them are turnovers anyway, but I'm not buying that carrying is the most important stat just yet.

I'd say Agility - Speed/Strength - Vision - Carrying - Footwork, and of course if he's your primary runner, Stamina helps too (although again, Singh did fairly well for himself with just 4 Stamina as my primary runner)