When you buy a Miata, avoid the special editions. Why? See, you'll fall in love with the car, and when you own a special edition, every little scratch, nick and ding sends you over the edge. You'll end up storing the car rather than driving it. Get a regular Miata with cloth seats and drive the hell out of it. It can take abuse with a smile.
Handling and steering, top-down exposure to the elements, exhaust note, fun-to-drive nature rain or shine.
More power, bigger brakes, glass rear window, improved sound quality from the stereo...all the things Mazda did for the 1999 and newer cars.