The limited-slip differential is a key desirability driver, but owners distinguish types across NB2 years: the Mazdaspeed uses a Bosch Torsen while some 2003 NB2s (e.g. Shinsen) use a Tochigi-Fuji unit.
Torsen vs Tochigi-Fuji limited-slip differential
Mazda MX-5 Miata (NB) · variant