What levels faster in World of Warcraft, a Shadow Priest or a Rogue?

As someone who played both a rogue and a priest to level 70, I would say a rogue. Early on a rogue will level much faster than any priest up to level 20 when a shadow priest gets Mind Flay. Also, never underestimate the usefulness of Sap to fight multiple mobs. Also rogues get Vanish which is a lifesaver. I've heard Discipline priests are much better at taking damage and handling multiple mobs at higher levels, but this is only what I've heard.

Shadow priests can do lots of damage and can go much longer between breaks (kind of like Warlocks), but they still need to stop every so often for mana breaks at least as often as a rogue has to stop to eat or bandage. Rogues can often kill tons of mobs with taking minimal damage and can regenerate energy pretty fast. You spend less on food than mana drinks if you have good Cooking and you can pickpocket for even more stuff and money.

I admit I only played shadow for about 15 levels around 50 to 65, cuz I was a dope and wanted the challenge of leveling a holy priest.