To be honest I really hope all the English speaker would just choose to play on one side. The player population in TW is Thin, and i mean very thin, especially with westerners. I think it is not wise to split up. But i understand you should play what you are comfortable with.
In my opinion the alliance is a more logical choice, because there tend to be more horde already. and since there is only One pvp server this time if the population ratio goes out the window. There wont be much left to hold pvp together and people will just go back to retail to play horde vs horde. I know this because I can read other Chinese post and i know what state the BFA servers are in at the moment and how bad world pvp are in those servers. hell even BG queues are horde vs horde most the time. It is a very delicate and overlooked issue that i just want people to know.
All these are just my education guess so take it with a pinch of salt. and you can argue that i could be wrong. But statistic doesnt lie.
Sure the horde racials are better in pvp, but better players and teamwork trumps better racial any time of the day. Plus it would be nice to not wait in BG queue.
All that being said. If ultimately the majority of people i know are playing as horde, I may well be forced to play horde. But i really wish people could see reasons.