Kinka of Spinebreaker posts a question that I haven't seen anyone ask for a while; does the Horde really have more faction pride? Various reasons are this feeling are offered, from the lack of a strong Alliance-side leader (with Varian Wrynn feeling like a shoehorned, and controversial claimant to that position), to the less unified Alliance leveling experience, to more philosophical assertions from Filara of Terenas concerning early Horde differences continuing to exercise an influence to this day. In classic WoW, Filara observes, the Horde population on each server was typically small and outgunned. People knew each other, could network easily, banded together againt superior Alliance numbers in world PvP, and -- when battlegrounds became available -- could typically get games significantly faster than their Alliance counterparts. Add the numbers up and it's easy to see how faction difference became part of WoW's conventional wisdom.
What interests me more is how rarely we see this question come up nowadays. During and shortly after classic WoW, comparison of the two factions was both inevitable and the source of major fights on the forums. Despite being outnumbered on the vast majority of servers, Horde routinely encountered more battleground success -- or so went the popular theory. As BC went on and the Alliance slowly lost a bit (though by no means all) of its population advantage thanks (let's be perfectly honest here) to the influx of Blood Elves to the Horde, it's possible that some of both factions' finer "cultural" distinctions have been somewhat eroded, if they ever existed at all.