I have only driven the Miata, Z-car, and the S2000, so take my opinions with a grain of salt.
With the Mazda or the Honda, you will have to budget about $1000 for a proper roll bar if you want to go racing, and depending on the application, you may lose some DD-friendliness. Much like you, I didn't fit in the S2K worth a damn, so new seat rails, or racing seat would be 100% necessary (and the stupid, non-adjustable steering wheel). Beyond that, both are pretty solid little racers in terms of durability. However, earlier AP1 cars tends to be oil burners at high RPM...
The Z is the big girl of the batch, but can fit so much more tire front and rear than the other two that it's pretty easily compensated for. Ideally, you would be looking at 08+ w/ the limited slip diff, because of the beefed up engine and trans, but $15k leaves that just out of budget I think. For any 350/70Z, brake ducting, and various coolers are pretty much necessary to get consistent performance out of it. Go figure, big engine + small engine bay = heat. Also, it was definitely the best car for daily driving, I drove an 08 Touring(?) and the extra torque compared to the S2K/Miata was immense, and it had excellent gears for cruising, and good overall street manners.