Between Norwood and Calhoun, my uneducated opinion is that if their situations were reversed; Calhoun was in Atlanta, Norwood backing up KJ, this discussion would be much shorter.
They both have size issues but Calhoun was considered a better prospect in almost everything I read pre draft. It's just the spot Norwood landed in that got him a boost.
In dynasty drafts I almost always go with talent over situation. Situations change, but talent will eventually get a shot in most cases.
JJ Arrington is the player that flashes in my mind when I think of these situations. Before the draft last year he was an interesting prospect but barely made the top 10 in pre draft RB rankings in most I saw. Then he goes to a great situation and becomes the consesus #4 RB in rookie drafts. Now he backs up Edge. Bad situation, bad #4 pick. Easy to say in hindsight maybe, but there were warning signs.
I obviously can't say Norwood is the next Arrington but I don't have a good feeling.
I would personally take Calhoun (and Drew) over Norwood. And depending on how the Droughns/Green/Suggs thing plays out, I'll be watching Harrison closely in Cleveland too.
Sorry, just babbling to kill time til Bloom gets here...