The food at 50s prime time is definitely better quality--Sci Fi is a bit more like quick service food and is mostly about the atmosphere.
For Tusker House, you will typically see each character once. We have eaten there many many times, and Tusker House is always crowded. The only times we've had character meals where a character visited twice are when a restaurant is really empty, and Tusker House never is. I thought the breakfast food was pretty good, though I don't love it the way some folks do, but I would definitely eat there again.