This isn't a knock against Wes Welker, who despite the messy breakup, is still one of my all-time favorite Patriots. In addition, I'm not even basing it on "clutch play" in big games, which I think to some degree is more about perception and small sample sizes.
I believe the Julian Edelman is a better wide receiver than Wes Welker ever was, based on his skills, period.
Here are the main reasons, in order of importance:
1. Catch radius. The most important reason why Edelman is better is his catch radius. Despite being on paper just 1" taller than Welker, Edelman plays bigger. He seems to have longer arms and can cover more ground in a shorter time. There are very, very few times where Brady throws a ball over Edelman's head or where a ball is just out of reach. It also makes Edelman a better red zone threat. On the other hand, as good as Welker was, the ball always needed to be placed within an inch of the target. Do you remember how many busted screen plays were the result of missing a connection with Welker?
2. Hands. Welker also had his share of drops on wide open passes. Because of his high number of targets, I always felt that people would too harsh on his drops, though in later seasons the problems got worse. Still, Welker often needed to use his body to catch balls. Edelman rarely drops passes and is able to snag balls out of the air using his hands only.
3. Strength. There is little doubt that Edelman is just plain stronger than Welker. Welker could be shut down (often in the playoffs) by getting jammed at the line and just pushed around. Edelman is just better at fighting jams and releasing off the line. In addition, with the ball, Edelman is not only shifty but is also tough to tackle as he has a great center of gravity and uses great strength to stay up. Welker was also extremely shifty but was forced to rely only on the quickness. Edelman uses both quickness and power to move forward, and he will drive himself into a player to pick up that extra few feet for a first down.
4. Straight Line Speed. Welker was rarely used as a vertical threat because while very shifty and quick, he was not that fast. Yes, he could accelerate very well, but his top gear did not often get him behind defenses. Brady is able to use Edelman as a deep threat more often because Edelman is faster.
All in all, I would say Welker in his prime was slightly shiftier and quicker than Edelman, but for the reasons above, Edelman is a better overall wide receiver. It is amazing to think that the Patriots almost let Edelman walk after 2012 and that the Amendola vs Welker debate was so controversial while Edelman was an afterthought.
