I drove RWD sports cars exclusively for 13 years, never ran into any condition the car couldn't drive through. If I wanted to go somewhere I went, no matter what the conditions and even when other drivers were getting stuck. RWD is not any kind of impediment. In fact, snow storms / ice storms is where they shine!
Yes, the entire auto industry and the laws of physics vs. you. RWD is not crippling by all means but FWD cars have a clear advantage in snow and ice, and wet conditions due to better traction. What RWD is better for is transfer of power and durability. That's why you pretty much only see it in sport vehicles and trucks.
As for OP's question - Miata is a toy. So if you want a toy go for it. If you need a practical car, stay with the 3.
Quick word here though, I work with cars, Mazdas are probably the most rust prone vehicles I have ever seen. Especially the Proteges and the 3s.