Orgrimmar feels like a military outpost with a few specialist zones.
Thunder Bluff feels more like a city-in-the-making than an actual capital city for a whole race. I’d like to see TB grow up to be the social hub of the Horde while Org stays the military hub, honestly.
Silvermoon is gated behind portals and zoning, but is the best City the Horde really has – a shame half of it is a starting quest zone.
Undercity was and still is the most confusing city layout in the whole game. Even if you consider it to really just be the dungeons of the Lordaeron Palace (a better description than the sewers, IMO), it’s cramped and samey wherever you go.
Compare that to the Alliance:
Stormwind really does feel like a city condensed into the highlights an adventurer cares about. The architecture is solid, the layouts can be annoying, but make sense, and it’s gotten so much love over the years that it feels like a city that is and has been lived in by the Alliance.
Ironforge feels like a military stronghold – not an outpost that grew up, but a real stronghold that has been developed over countless years into efficiency. It’s a circle, but each district has a little bit more of a distinct feel than Undercity, and it feels wide and spacious like a city ought to. Ironforge is established and designed as an actual city.
Darnassus is crazily well built for how young it is (less than 4 years old at the start of Vanilla), and shows that Orgrimmar could have conceivably been made into more of a city if the Orcs (or Blizzard) had wanted it to feel like more of a city. Lore-wise, the Orcs could have established a more cultural city than a military outpost, but they didn’t.
Aside: The Echo Islands even hint at this – in the three years from Vanilla to Cataclysm, the Trolls are working on starting a city at the other end of Durotar that is a little more home-y and comfortable than Orgrimmar (and only partially because Garrosh didn’t want Trolls in his city). I’d love to see what the Echo Isles could become given more time, and what Orgrimmar could become under a non-war leader and time to develop.
Back to the Alliance, the Exodar is the worst city the Alliance has, IMO. I understand that, like Undercity, it wasn’t designed in lore to be a city, but a spaceship, and it captures that feeling well, but that feeling isn’t something i consider to be a great structure for a city. That said, there were some good scenarios that showed us how it works as a dungeon.