This is like asking whether you'd prefer to drink varnish or paint.
I'd take Owens without much thought. The biggest knock on either one is the locker room division, but Owens has usually remained quiet if there's a veteran player who's willing to keep him in line behind closed doors. He wasn't any kind of a distraction early on with Steve Young and Jerry Rice around.
Moss, on the other hand, doesn't now and never has acted that way. Cris Carter, Jake Reed, and Randall Cunningham couldn't get him to exert maximum effort early on. Don't forget that when he had a slight muscle injury a few years back, he played one snap of several games to keep his consecutive game streak alive rather than sit out for a week and let someone who could actually play that week get on the field.