We have all three chains in our area. Buca Di Beppa runs rings around Olive Garden in terms of food quality and taste. Carrabas is also highly thought of and many would opt for Carrabas over Olive Garden. Having grown up with a live-in Nona (Italian for grandmother), it's hard for me to enjoy anyplace's red sauce or meat ravioli, etc. etc. At least at our Buca, I do like their red sauce, and usually enjoy their specials much more than their regular menu items.
I don't know how the restaurants compare to each other in the Orlando area. I did have the opportunity to eat at Macaroni Grille for the first time in December and that was very good, but it is like an Olive Garden, BDB, Carabas. Other Italian restaurants we've enjoyed are Palio's and Portobello yacht club, both on WDW property.
What you may want to do is to look up the Orlando Sentinel's Foodie Awards. Last year we found a good Korean restaurant via that resource.