I have an MX3 and a Miata. I'd get a Miata for the money, allthough I prefer the NB over the NA and NC models.
MX3 doesn't feel like a miata partly because of the heavy weight of the engine and more understeer. If you have a proper alignment with the MX5 the steering becomes super precise and because of the light weight and 50/50 weght distro it has an easier time getting around the corners.
I love my MX3 though, Great for hauling stuff and a lot more comfy on the freeway. Both cars have a close 1st/2nd gear that makes it a bit slow at the lights. Miata gives you a lot more confidence than the MX3 when your driving it.
If you were going to get a miata now, it would probably be an NA for that money. They don't handle quite as well as the NB, but the NB is also more refined a little heavier whilst the NA is noisy, has worse brakes and is less rigid.
Anyway, good luck with whatever you chose, I love both my MX3 and MX5, allthough my MX3 has been neglected the last few years, I just started taking care of it and will be rebuilding the suspension
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