I think we are simply trying to say that Moss has been more IMPRESSIVE this seasons. Sure, Welker is getting a ton of receptions and yards, been when have you EVER seen Welker make a ridiculous catch, dominate in the Endzone, or abuse pro-bowl CBs? If Moss got to lineup in the slot every game while having another #1 receiver wide, he would be impossible to stop.
Also, I don't think you can say "Welker makes Moss better too". Really, how? Point to me games and plays where DBs decided to double-cover Welker rather than Moss. They don't. The only time a safety will go with Welker is if A. He is jumping a route, B. He is in a short zone, or C. He blows his coverage.
We can point to TONS of plays where Moss drew the safety, opening up the middle for Welker to make a catch. It happens all the time, but the opposite almost NEVER happens.
Take Moss off the team and pit Welker against pro-bowl CBs with safety help and he WILL get shut down. He's the best slot receiver in the game and is a great "short-yardage" receiver, but he's no Randy Moss.
This is a little heavy for me but I agree with some of your points. For the record, I voted for Welker mostly based on recent performances, but Randy Moss is certainly capable of taking that crown back of WR most deserving of Pro-Bowl this week. I think Welker would produce just fine against the top cornerbacks of the opposing team - he'd probably have about 80%-85% of the receptions he currently has which is still really good. Moss just allows him to go to the next level.
I think they both have a good chance of going to the Pro Bowl.