From the free car park by the viaduct I did the wall in 1hr 10 and that was pushing quite hard for me. I don't "train", just ride 2 or 3 times a week for fun. To do it in an hour from the Afan Visitors Centre car park you must be seriously putting in the miles and I imagine you compete?
Whites is a little longer. Maybe 1hr20? I manage W2 in just over 3 hours when I've been keeping up the riding.
I think the Wall has a much better descent than Whites. I can happily deal with the fire road bits for that. Whites climb is much better as it's most single track and a bit more techy but the descent is crap. Its all roughed up and its difficult to carry any sort of exciting speed. There's some jumps in it, but for some reason they seem like they're built uphill. Probably the worst though out section of the trail.