Nostalrius Begins - Quality wow vanilla realm (1.12)

hi, i started playing on nostralius since 3 days ago, i made an orc warrior who is lvl 15 atm, but im thinking about rerolling to mage or warrior character in alliance because i checked on armory server and i found out there is not many hardcore guild in horde who cleaned MC and onyxia compare to alliance guilds, sadly they’re is no “change faction” option
so i would like to know with which class i’ll have less dificulties for leveling,and for pvp/pve HL.

More Horde guilds are up & coming, so you don't need to switch factions, IMHO.