I think Ul'dah is so popular for a couple reasons. For starters, we've heard and seen so much regarding Limsa Lominsa so far and people are quick to jump at something "new."
Ul'dah also comes off (so far) as having less of a narrow theme to it. With Lominsa, you've got basically a bunch of pirates and fishermen. Gridania seems heavily focused on nature (plants, animals, etc). With Ul'dah you've got pit pights, powerful aristocrats, and possibly back alley thieves. It's made even more appealing due to the mention of a "sultan" and the Alladin-like Arabian mysticism.
Ul'dah also comes off (so far) as having less of a narrow theme to it. With Lominsa, you've got basically a bunch of pirates and fishermen. Gridania seems heavily focused on nature (plants, animals, etc). With Ul'dah you've got pit pights, powerful aristocrats, and possibly back alley thieves. It's made even more appealing due to the mention of a "sultan" and the Alladin-like Arabian mysticism.
