I'd have to drive them both to see what they're like, but there definitely are a lot of Z's around.
I imagine the Z is heavier, but it has some more power, and the RX-8 is suppose to be fairly agile and it's pretty unique looking. Very hard to answer actually.. I want to say both because they each have their good points, but I did sit in a few Z's when I was shopping for a car and I found it hard to see over the Hood
since the seats were so low slung and I am like 6', but maybe the just needed some adjusting.