Orgrimmar is a busy, crowded, laggy city. Most people I’ve seen keep their bank alts there; a minority uses Silvermoon City (which I could never understand; the bank and AH aren’t very close), Undercity (depressing and annoying to move between the bank and the AH) or Thunder Bluff (where the bank and AH are pretty close). I used to keep my bank alt in Thunder Bluff myself – then, when 4.0.3a hit and reset everybody to a random location, I found myself in Orgrimmar and decided I couldn’t be bothered to move. So I went exploring, to find the best place to be in the shiny, brand new Orgrimmar.
The thing is – there are five auction houses in Orgrimmar now. Similarly, there are five banks.
The first pair is in the Valley of Strength, where it’s always been. They’re further away from each other now, though, and it gets annoying to run between them repeatedly.
The second pair, in the Valley of Honor, isn’t much better in terms of running distance. The third pair, in the Valley of Wisdom, is a little bit better, but still somewhat far.
Then there are two pairs in the Valley of Spirits – one for the goblins, and one for the trolls.
The goblins have their bank and their AH set up quite close to each other; the mailbox is a bit further away, in what seems to me an incongruous position.
The trolls have set up shop in one of their buildings. The mailbox is at the bottom, while the banker and auctioneer are at the top.
Which you use mostly depends on your preference.
Personally, I find the goblin area irritating to look at, and the few steps between the bank and AH coupled with the mailbox distance and the NPC crowd around the area annoys me.
On the other hand, I easily found a position that would let me access the troll auctioneer, bank and guild bank without moving a step; when I need a mailbox, I jump off the building to get to the one that’s right at the bottom, then climb back up.