This of course depends, but in short
- Level 80, first to go into the new zones
Stormwind, use the new Inn in the back of the dwarven district, this is going to be the new hub, there’s a breadcrumb board, close to the “Island of Portals” and once you have old world flying you’ll never need to go near the front of SW again.
- Level 80 slacking Toons
Ironforge, close to the action but not the major lag hub Stormwind is going to be.
- Banking alts
Two choices, Stormwind at the Dwarven district end, or the Exodar (low populatation, low lag).
Wherever makes sense for levelling. Travel is far far less painful than it was.
Of course the bottom line is “whever you think makes sense for your playing”, but personally I’m going to be moving my tankadin at the weekend to Stormwind (only a short ride back to his favourite inn at Ironforge) ready for the push against Deathwing.