WHAT TIMELINE?

[Hmoffett]

Just got a allied race, started level ten and I'm at the part to choose what time line to go to. is it all the same, or is there one faster then the next?

[ZG Support 1]

According to a WoWHead post one expansion can be faster or slower than another. How accurate that is can be debated and Blizzard is still messing with leveling times on the test servers so it will all probably change soon. Supposedly between the 8 different expansions the leveling times range from 12-24 hours to hit 50. So for a casual player just doing a few hours a day they should be able to hit 50 in about a real week of playing no matter which expansion they pick.

All that said, pick the expansion that has the story line that interests you the most and enjoy your time playing the game because once you're at max level you've still got a couple more months until you can get those last 10 levels.