For foodwise not even a close comparison, Mama Melrose all the way. It's also just a wonderful restaurant altogether.
However, my DS loves SciFi and has asked to eat in the "cars" again this trip. So we may try it for lunch (great cheeseburgers) or even just dessert as there were some wonderful ones on the menu and the atmosphere can't be beat.
I don't think you can compare these two as there are two very different ones. Try lunch at SciFi and dinner at Mama's.
Also Sci-Fi does not do FDP. Only Mama's, Hollywood & Vine, and Brown Derby.