kickoff returners. Punt returners have to be able to dodge the first man or two, and if they are going to gain yards, it's mostly by juking players.
Kickoff returners get a running start and are pretty much up to speed by the time they have to confront tacklers. Sure, being good at changing direction does come in handy (see Austin Collie's best returns, for example), but really straight line speed is quite a bit more important for returning kickoffs. If a KR does much dancing around, he isn't going to have a very good return in most cases.