The one downside is that, because it is the largest server, you may be subject to server lag, and reduced FPS in crowded areas like Valdrakken at peak times. Personally, I haven’t found either of these troublesome, but your tastes may be different.
and sort by Horde population.
If you want a slightly smaller server to avoid the size, I’m not personally sure which of the next couple to advise, since I don’t play on them myself, and most of what I used to read about them may be out of date, but when I was choosing a Horde server, each of them had some feature I avoided - Twisting Nether had a significant amount of non-English speakers langages, and I read Kazzak had a less friendly element.
If you want to go down a small step in size, I’ve always liked Stormscale. It’s still decently busy, though not nearly as busy now as it was at its peak, and depending on your playstyle you might find that a good thing.
Whatever your shortlist, I recommend making a level 1 and running to Org and logging in at prime time to get a feel for the place. Most people are in Valdrakken now, ofc. but you can still check out Trade chat (once you leave Services channel so you can read anything! ) and chat with guild recruiters and soak up the vibe. It’s a lot less hassle than transferring or rerolling later if you find you dislike something.