I love both, but currently couldn't own either. Not without more time, more money and a well-equipped garage.
240Z
1970-1973
2.4L inline-6
150 hp @ 6,000rpm
148 lb-ft @ 4,500rpm
Curb weight 2,355 lbs

For more of the Z lineage:
http://www-scf.usc.edu/~beadles/
RX-7
1978-1985
Twin Rotor 12A (1.14L)
100bhp @ 6000 rpm
105lb-ft @ 4000 rpm
Curb weight 2,420 lbs
If I was choosing between the two, I'd actually go against my rotary-lust and get the Z. What about you?