The Pandaren are more Alliance-oriented, and i'll explain why. First of all, they were close allies of the Night Elves back in the day, but they severed their ties due to the Highborne's magic addiction. Now, i'm kinda shooting myself in the leg here when asking for Blood Elves and Nightborne on the Alliance. If we pretend i didn't, then the Pandaren are more likely to be drawn to the Night Elves (who are now nature-lovers and only have a small faction of highborne within them) than the arcane-obsessed Blood Elves and Nightborne. Furthermore, they share a lot in common with the Ironforge Dwarves, from their love of brews and good food to their love of tales and friendly brawls. On the other hand, they waged a war, back in the old days, with the Zandalari, which were allies of the Mogu (the Pandaren's most hated enemies), called the Zandalari Troll wars. They do have some in common with the Horde when it comes to spirituality, as their geomancy is very close to shamanism. But, i find it more hard for them to have common grounds with the evil Forsaken, greedy Goblins, voodoo-inclined Trolls and warmongering Orcs than the races of the Alliance. Sure, they won't be attracted to Void Elves (as the Sha was a major threat in Pandaria), and maybe even Dark Iron Dwarves (as they used to ruin Brewfest). And maybe the Kul'tirans still hold a grudge for Chen's involvement in killing Daelin (though, they forgave Jaina), but it is still pretty minor, in my eyes, in contrast to the Horde races. Plus, they're all about peace, meditation and controlling their bad emotions, which the Horde struggles to do.