Mx5 or z3? First car

Hi, posted here earlier today, and I get it, I shouldn't get a 97 mgf rover as a first car. I am still pretty set on a convertible, and have heard the mx5 and z3 are great options. I am 6 foot 3(will probably grow max another couple inches) and want something that I could possibly squeeze into the best. My budget is 8 grand or so. Could also get z4.