Edelman has better numbers is the 3 cone and short shuttle drills, which would lead me to believe that he has better quickness than Welker, he also has better straight-line speed, he actually has better numbers all over the place.
Julian Edelman*|*Kent State,*WR*:*2009 NFL Draft Scout Player Profile
NEW ENGLAND PATRIOTS, Wes Welker , Julian Edelman, Randy Moss, 40 YARD DASH TIMES
What I think your eyes are interpreting as quickness are the better angles and shifts that Welker makes, which allows him to evade defenders. Knowing how and where to move can be just as if not more important than the ability to move.
I believe Edelman can gain a better understanding of field geometry with more playing time and dedicated practice with TFB, it's possible that he even surpasses Welker in terms of playmaking ability.
Regarding a big-time WR and our SB rings, I don't think that's a sound argument, keep in mind we had a lights out defense during those years and more experience in the skill positions. Many of our WRs and RBs are relatively young, and the O-line will have a green rookie in Solder, these moving parts are more likely to make mistakes and put our aging HoF QB in danger, having a Larry Fitzgerald/Andre Johnson on the field can make things a lot easier on your offense.
I'm not suggesting we grab a big-name WR because 'everyone knows you need a big name WR to win" but rather I'd like a WR whose ability creates a lot of impact on the team. A guy who can work the outside and deep zones would make things tougher on opposing defenses, a guy that can box out a DB and go up and make the grab would help out a lot, the deep ball is one of the weakest parts of TFB's game, a receiver that can compensate for that would definitely make a difference.