I think Edelman, mostly because for every week that Welker is out, there's a very good chance Edelman catches six balls just by the nature of where we'd use him. As such, he may build up a lead in the first few weeks and coast from there.
Honestly though, I'd be happier if they all have about the same number. Would bode very well for the versatility of the offense if five young receivers each chip in with 60-70 catches while Moss gets his 80, Welker his 100 (or prorated equivalent), and Holt chips in with 50. My math may be way off on what's possible, but you get the idea.