My step son has a Miata hard top convertible touring edition. It has 6 on the floor transmission, very tight handling, and is a lot of fun to drive but way too small for my taste. He loved it at first but now wishes he had something bigger just because it is so small with no room to haul anything.
Don't know anything bout the Subaru and I haven't played with Miata RF.
I have owned three Miatas and still have one. It is my wife's car and she has been driving it since 1995. All three cars had zero problems. Other than standard maintenance there has never been a repair bill.
My brother has a 2008 Miata with a retractable hard top he has been driving for 10 years; again, zero issues.
I can say that Miata are good solid and reliable cars. Plus they are a blast to drive.