Never had the sugar free, so I don't know. I would think they'd have to tell what sweetener is used, as aspartame cannot be digested by phenylketonurics. I am severely allergic to it, and it gives me horrible migraines.
You did try two flavors I've never had, though. Favorites here (or were, we don't have Rita's nearby now) Mango, Root Beer, Cherry, Raspberry and mine was also Pink Grapefruit.
Ahhh, to have a gelati right now. I LOVE Rita's!
Suzanne