I do like a lot of Gracie's shirts...and shoes and hats. Ables has some great stuff though. Tough one. I think I'd go Gracie for the more unique designs
I think i'm gonna go with the able sisters, as much as I LOVE the gracie designs especially the ones for the sweets set it's incredibly easy to buy all of her clothing (not price wise of course, LOL) but I mean to have her whole collection since she sells the same things seasonally. Whereas with able sisters there's always different items that you can buy each season and nothing is really an exact repeat of what you've seen in the last 5 days. I also prefer the able sisters as characters to that of Gracie, sometimes Gracie's dialogue can be hilarious but most of the time she's unnecessarily sassy.
EDIT: Accidentally voted gracie grace, but you get the drift.