I think over long distance Bale is the fastest, over the short distance Lennon is the fastest. I can't really tell to be honest, all three of them are absolute speedsters.
That assist he provided for VDV in the Blackburn game is definitely the best example, he passed it to Adebayor, who held it up for a few seconds, then flicked it behind him for Walker to dash around the nearby players and set up a tap-in. All three of them are very dangerous in open space because few players could catch them, let alone defenders.
Vedran is a better defensive fullback, he is bigger and a better tackler, what I've noticed about Kyle is that even if he gets caught out his pace and work ethic allow him to make up for it and often catch the player that makes the break and clear it. He is definitely maturing, at 20 years of age he has a significant amount of improvement in him.