Can't answer for horde, but my ally toons hit 60 in a bit less than 10 hours played:

1-10 quest
10-16 Deadmines
16-22 Stockades
22-40 SM
40-45 BRD (worst part of all the boosting)
45-60 Scholo

Stay in SM as long as you can as the exp per hour is the best for the entire 1-60 journey.