AB is a different beast. Again, I think a good comparison (at this stage of his career) is Steve Smith. He can be an absolute ****ing headache if your plan is to put your #1 corner on him (think 2014 AFCCG when Smith burned Revis and see last weeks performance of AB vs. Gilmore).
If you have a corner like Ramsey, Alexander, or Lattimore, they're going to be able to cover more traditional players like Evans or Godwin. But AB is really quick. When he's healthy, he's going to be a huge problem out in space.
What AB doesn't do as well, partly due to his small size, is provide consistent, mid range targets that move the chains. He isn't, like Godwin, a guy who can use his strength and size in the middle of the field, extend/push for those extra three yards for the first down. He's not very good on those quick screens either. He's a lot more boom-or-bust.
But just to show the difference, look at the height/weight of these guys. AB is 20-25 pounds lighter and 2-4 inches than them (besides Diggs, who is indeed more similar to AB as he relies more on quickness).
Allen - 6'2", 211
Cupp - 6'2", 208
Godwin - 6'1", 208
Diggs - 6'0", 191
Brown - 5'10", 185