Someone once did a comparison of all the zones & instances and how easy/difficult it is for Alliance and Horde to get there, they are actually about even all things considered.
I was just talking to Suvega about how, even on a PvP server, horde can instance level 8-45 without ever hitting a PvP flagged area. (WC, SFK, RFK, SM, RFD)

Alliance get Deadmines, Stockades, and Gnomer, which will (at max) get you to level 33.

Contested: BFD, Ulda, and onwards (ZF, temple, etc)




Horde have it way better for instance leveling and/or powerleveling (boosting). Having to traverse into horde territory to make up for the instance level gap, and finding your lowbie self camped at the meeting stone by a level 70 powerleveler... it really, really sucks.