I'm currently an Orc and felt the need to meet up with my fellow kind. Any specific Strongholds that are better than one another?

Not that I have seen. All have a armorer and an alchemist. as well as a possible companion.

They don't really have too many differences. I know one of them borders to a mine, which may be useful, and in one you can start a daedric quest (not exactly which stronghold though). There are also some skill trainers in the strongholds, differing per stronghold.

Not really... Maybe Narzulbur (has a ebony mine associated) or Largashbur (has a nice quest - The Cursed Tribe - associated)