Re: Trying to make a decision between a couple of cars...
I owned and autocrossed an RX-8 before I bought the XF.
They are somewhat similar in performance capabilities, but have a very different feel. In "normal" driving, the XF feels faster because of its big low-end torque advantage. When driving each to the limit in a straight line, there's little difference on the stopwatch, but a big difference in the feel.
Once the road ceases to be straight, the RX-8 is a clear winner...better steering, better F/R balance (and I would guess a slightly lower CG, given how low that tiny rotary sits vs. where our big V6 is), and lighter overall (at least comparing base to base), and a great LSD. There are good reasons that the RX-8 is in a significantly faster stock autocross class than the XF.