If you really want to experience something new, then I'll say MoP is for you. Try the Pandaren race, the only race (so far) who could choose faction later, or the Monk class, which I think any race can be (warrior, anyone?). Or just make a Pandaren Monk and worry about faction later. ;)
A fair warning, however. Like Kelthuzzad mentioned above, MoP is pretty much beta atm (at least in private server), so many things are still not working, and I'm not sure how much raiding you'd be able to do in MoP as of now (I'm still pretty new to MoP). At least some raids are working, and if that's good enough for you, then welcom to MoP! :D
Otherwise better stick to Cata..