I prefer 10 because rogues can completely dominate. At level 15, warrior starts to shine. I love my 15 war and my 10 rogue. Either one a rogue is a solid choice, but rogues at 10 just deal a sick amount of damage compared to other classes.

I've also noticed that 10 seems to have the best community for 1v1 play. However that may just be a result of everyone wanting to duel me since I've got the top level 10 rogue in the game.