Tutto Italia if those are your only choices! Been a while and I only went once to Tutto Italia in 2008 and Mama Melrose in 2009. Based on that, the service and quality of food was many, many times better at Tutto Italia.
There's just one thing that bugged me... Tuttu Italia said the coffee (regular coffee) was not included as a drink on the dining plan. I just thought that was weird. And it's just a dime a dozen Italian restaurant and we have plenty at home. I like other restaurants in Epcot better -- Coral Reef, Chefs, Marrakesh, Biergarten, San Angel.
Tutto Italia is expensive too if not on the dining plan. For that pricing, I'd rather eat dinner at Flying Fish Cafe at the nearby Boardwalk Inn. On the dining plan FF Cafe is 2 credits.
But the main reason I'd pick Tuttto Italia is that, in Hollywood Studios -- I'd much prefer to eat at 50s Prime Time (food, shakes, fun joking around) or Brown Derby (food much, much better than M.Melrose). I'd even pick SciFi Diner over M. Melrose, the food isn't better but DS likes dining in the cars and I think it's kind of fun too.