The S2000 is an EXCELLENT car but, bear with me a moment, speed isn't always everything...
The Miata is about 400 lbs (180 kgs) lighter than the S2000. This perceptable difference in weight, coupled with the Miata's excellent nimble handling gives it an early British (or Italian) roadster feel--not necessarily superfast, but all-around fun car to drive.
I think the Miata is best experienced in a place where there are roads with alot of hills and twisties (preferably tree lined in the fall). I'm currently an isolated flat-lander which is why, two years ago, I went with the BMW z3 coupe -- I really liked the style of the coupe (also, I don't think the flatlands aren't particularly great for convertables either) and it had good handling and acceleration. Besides, the S2000 at the time was still commanding a $3-5k above sticker for "market conditions" at the time and I just couldn't bring myself to give the dealers the satisfaction. (Note that I also test drove the Audi TT and Porsche Boxter but in comparison to the Miata, Z3 and S2000, these things felt like tanks).
If I were buying today, still stuck in the flat-lands, and wanted a convertable, I would probably go with the S2000.
If I were in New England, I think I would lean toward the Miata (or maybe an old Triumph TR4A).
Of course, to each his own...
