T.H.
I used the traditional ones until my kids could move and then took them off. My daughter pretty much stayed put and rarely got herself caught in the slats so it was fine. My son however, was a maniac in there! I ended up buying a breathable bumper and it was awesome! I couldn't have slept without it b/c he was constantly getting hung up! If you don't care so much about the cutsie bumper stuff I'd just get a breathable one.