>>28563934
Stock for stock they're quite close. The RX-8 is heavier, and you feel that. The suspension differences I'm not going to argue, but I think the RX-7 outhandles the RX-8 a bit due to the weight difference, among others. The RX-8 is probably the easiest car to drive you could ever get though, which helps 99% of people achieve better laptimes.
RX-7 feels a bit more agile. I wish it had the same HP but was NA, because revving out an NA rotary like in an rx-8 is amazing (and it's a lot less bullshit to deal with).
If you get an rx-8, get the lighest version possible (base spec, no leather, no sunroof, etc.) I've had one of those and an R3 spec and although the R3 felt a bit more planted, it was also a bit heavier, and the car is underpowered as-is so the last thing you want more of is weight.