Best way to know is to just try it really. Levelling is fast as you may know so not a big time investment needed.
Players from different servers have different experiences.
I do think that Horde in general are more organised and more skilled when it comes to bg's. I get the impression that the more skilled players tend to go for the, what a lot of people consider to be the cooler looking races and faction, Horde that is. If you look for instance at the pvpvideos on wowmovies, most of the time it's Horde players.
Most famous pvpers play Horde as well.
Edit: while undead rogues look cool, it's overdone. I think female night elves are the coolest, they have the best animations imo.