Due to the legacy of the old Horde that the new Horde has, we find the lore of certain Horde race confusing and depressing. There is one of the interesting, fun thing about world of warcraf is to play armchair historian for the fictional setting. In the case of the Horde the twin pillars of the post-Thrall era of the Horde seem to be reconciliation with the past and the forging of the future. Of course, each race within the Horde goes about this a different way.
   In the game, Tauren is the favorite. They are not only one of the most spiritually contemplative races in the game, which the only race to have both Shamans and Druids as player options but they have held on to a relatively calm mindset for generations even in the face of constant attacks from centaur trying to drive them out of their ancestral lands. Of late, the tauren have abandoned their nomadic ways for the most part and settled in Thunder Bluff, a city built with some fairly impressive mechanical achievements that shows there is more to the tauren than nature worship and ancestor reverence. There is also a dark side to the tauren, as shown by the Grimtotem tribe. In fact, these guys are the heart of the New Horde; aware of the past but looking forward, and their influence on the orcs and trolls has been a good one. If they have a serious flaw in the new Horde, it is that they are often willing to just go along with what others are doing without really making sure it is a good idea. They are less active and driven than orcs or trolls, far less vengeful than undead or blood elves.
   Still, the Tauren are the favorite and the will of Horde is the orcs. The very Horde concept comes from the time of the Burning Legion's manipulation and enslavement of the orcs on Draenor, and the fact that the orcs continue to organize in this fashion and are still led by a Warchief indicates both that they haven't forgotten what happened and that what happened has forever changed them. Right now the orcish internal struggle seems broken up into three basic elements, each represented by a major lore figure. The Warrior spirit of the Horde that seeks battle is personified by Garrosh Hellscream, who leads the Horde expedition in Northrend. The orcish desire to reclaim its past clean of Burning Legion corruption is represented by Thrall. And High Overlord Saurfang stands as a symbol for those orcs resolute in the face of their own awareness of what terrible atrocities have been committed in the Horde's name to ensure that this new future does not repeat the mistakes of the past. In Wrath of the Lich King, Saurfang has gone from a generic badass with a litany of quotes on the forums to a deeply realized, conflicted badass. In a lot of ways the work done on expanding the Horde storyline in Wrath is another reason to playing the faction, you simply ca not deny yourself the pleasure of the Wrathgate storyline from the Horde perspective.
   As a group, the Undead have some of the most horrible quests and any group that casually poisons nominal allies to death just to see what happens is not a group. That said an unrelenting will to exist and having united under the charismatic figure of Lady Sylvanas in record time. The fact that they have managed to organize into an actual nation in the ruins of Lordaeron is evidence to anyone that no, they are not the mindless horrors the Scourge often is. This would necessarily be of comfort to the living humans of Azeroth, however, just because that horrible walking corpse remembers you, it does not follow that he is any less dangerous. Still, the Wrathgate questline gets one of the worst vipers out of the Forsaken's nest, and assuming Sylvanas can move past the self-recrimination of having actually trusted someone that untrustworthy, the Forsaken have a real shot at revenge at Arthas through their association with the Horde, and Sylvanas has the chance for an actual Alliance of equals with Thrall now that the two have fought side by side. The undead are also the ones who brought the Blood Elves into the Horde, and as a result the Horde owns almost all of the northern Eastern Kingdoms, everything not under Scourge control anyway. The Forsaken are in a real position of power, and yet paradoxically are the most vulnerable they have ever been.