Are the factions evenly spread, or is there one dominant faction?
There are a lot more players on Alliance. Don’t let that dissuade you from playing the Horde however, should that be something you want to play.
It’s an RP PvE Server, those are usally somewhat skewed towards the Alliance in terms of player numbers. I agree with Terenak though, I wouldn’t put too much thought into which side is more ‘dominant’. Alliance might have more players, but that doesn’t mean that the horde has few players. There’s still a decent amount of us around and searching for a group tends to yield pretty quick results, at least during normal people hours.
Horde. 
Even though Horde population is smaller compared to the Alliance, it still feels comfortable enough to play and find dungeon groups.
The Alliance has dwarven ale and about 70% of the population is blond, blue eyed babes. Drunk white women EVERYWHERE!
And all the gnome hair you can eat! Try the green it tastes like apple candy. Goes great with our “blossoming” peacebloom production!
And when youre done melting your brain we have clean level streets so your walk of shame will be a safe one.
The horde has… err… Plenty of “natural body odour”. 