I choose 2.

Base: Fun! (early on it was challaneging and the quest wasn't grindy and was very varied content-wise.
Atma: I was lucky, but read the horror stories here on the forums (sorry for you bad luck players!). Personally I found it O.K. If it lasted long I'd hate it D:
Animus: It was O.K overall, it was pretty varied.
Novus: A loooot of gil needed... I didn't like it. I liked the maps though.
Nexus: ZZZZZZZZZzzzzzzzzzz was boring, but it was because I decided to spam trials. It looked like it's never ending.
Zodiac: I think it's okay, varied quest, different content. I have bad luck on this one, doing a lot of runs...