It is a funny thing about miata seats. In a miata they are great. When I had my Miata I never even thought about them. They seemed supportive enough, I never fell out of them and they never created any issues that made me even notice they were there. When I realized just how narrow they were I didn't hesitate to buy a set based on my previous experience.
In my fiat on the other hand they are totally unsupportive, ugly and uncomfortable. I hate them. They look goofy in an older car as well.
I think it must have to do with the reclined seating position in the Miata versus the upright fiat sedan.