It really does matter what time a day it is as far as solo queueing goes. Most people tend to party up regardless. It seems like horde and alliance are always trying to form premades, one side will hear about the others pre-made, and then they will try to queue into the opposing factions pre-made. It can be a little crazy at times, and it does seem like the alliance over all has a higher average of vet/f2p players on their team while the horde tend to have a few twinks here and there, but mostly levelers with pitchforks and white gear if they have gear at all. Oh, and tanks, like 2-3 tanks.
Tldr; it really all depends on the time, both sides can be equally challenging. Make friends with some people and it makes the game a whole lot more fun, don't be a dick who swears they are a God at 5 ability having pvp. Enjoy!
FOR THE HORDE!