It really depends honestly. I've had wonderful success recently going in the afternoon, especially with FOP since if you don't get there super early you're waiting, but a couple of times I've been left thinking that everyone else on vacation must have picked the same day to visit the park in the afternoon as me. I'll be at WDW again end of August and honestly didn't want to waste a park reservation for AK since I'm on a solo trip and didn't want to have to wake up that early, so I'll be doing the afternoon hop on at least one day. I always leave FOP for last since I can get in line right before park close and know I'll still get on without wasting my whole night and missing the rest of the rides just for that one.