I have one of each(Actually I have the skyline and my wife has the RX7)
R31 Skyline with a RB25DET (EMS computer, FMIC, 3 inch exhaust and Factory Turbo)
and a gen 1 RX7 with a 13B turbo (Microtech computer, FMIC, 2+1/2 inch exhaust and Standard Turbo)
both putting out around 180kw's at the wheels and I enjoy driving both of them for their different characteristics Skyline is great for its low down torque. and the mazda is great for its acceleration.
the big difference between them is about 300kgs. so my skyline has run 13.3 but I have yet to test the mazda due to Adelaide not having a 1/4 mile. But it definitely feels faster due to the weight advantage.