Well obviously the gunner dressphere with catnip kicks serious ass.
But I like the samuri or dark knight dresspheres the best. Probably cos i like the ideas between both of those in general. There's something about the responsibility and loneliness which attracts me to them and forms a connection with me i guess.
White Mage, Warrior, Dark Knight, Samurai. The movesets for all are really good, and I really find White Magic very useful, always gotta have a WM in a team! Darkness was a awesome move too, really did some nice damage.
I never even got the Mascott dress sphere, it looks kinda cool but at the same time dodgy to be a giant muggle and smack the hell out of fiends.
My vote went out for Flora Fallal, the transformation was so awesome that i had to see it in every fight I had, and so i did. The power of flora was so great that i couldnt ressist it. Although Machina Maw had a way better scene when doing her super attack.
My favorite dress sphere would have to be lady luck (it was an asshole to get) but it was well worth it.
My favorite part about it was the ability's like critical damage all the time gillianair double items and double exp.
All them ability's really came in handy to help me get to level 99 in a short time.
I really liked several of the dresspheres in this game, but one of them just has to be my most favorite ever. Alchemist. I found myself, once I got the dressphere, using it for almost most of the game. I felt more comfortable mixing potions and other items(it remind me of Rikku's limit in FFX) and being able to come up with useful items. And the attack power was pretty decent. Plus, the outfits the girls wore were pretty cool looking.
At the moment I like Beserker, Alchemist and Samurai
I have them all trained up on Lady Luck, which is very handy...and on this playthrough I'm trying to level them up at least 20 levels in each chapter...but using Lady Luck means that I'm missing out on some AP training...
Alchemist is massively useful. Of course, I'm barely 40% through the game. Stupid millions of mini-quests. I mainly use their default dresspheres - except for Rikku, she's the main White Mage. Paine is about 70% through her Warrior dressphere