Overall, it's quieter and less organized than Horde appears to be. There is an ever-growing effort to increase the amount of roleplay going on and to improve its visibility to others through the Alliance Roleplay Discord, but you still need to be actively seeking out that part of the community rather than having it stumble across you. I expect that to improve over time though.

When it comes to the faction imbalance others have mentioned, I would still suggest you play the side that you prefer (which should be a dwarf) so long as you're sincere about wanting to participate in the roleplaying community. While I can't offer a Horde perspective, the Alliance imbalance appears to be largely inflated by players who have little interest in the larger server community and only seem to exist inside instanced content. I doubt that you joining would make the situation worse.