Convenience: Cheapest average price to the other locations when teleporting and yes, there are a lot of people from our FC in Ul'dah as well as the other regions - they're fairly split. Which means that if we opt for Limsa or Gridania, we'll be forcing the people from the opposite location to spend a lot of gil indeed. Not to mention our FC belonging to the Immortal Flames, meaning we have to go there to top up on things.

It's perhaps worth noting that in the long run, I think we'll be able to get large housing for all three locations. That's quite a long run though. xD

EDIT: I'll say it again, I want your opinions of all three locations, not simply "Gridania." Especially if it's also your Grand Company and/or starter location.