I don't know about all this but I can tell you this much...
1. A LOT can be cleared up as far as accelleration and power issues with a tune and some bolt on's with the 370.
2. I've never had an RX-8 pass me on the track
In other words... any handling issues with the 370 can be cleared up with suspension and sway bars. As mine sits, it handles every bit as good as my Evo IX did... probably a bit better in fact.
In the end though it really comes down to personal taste. I wasn't a fan of the styling of the RX-8 (especially over the RX-7) but it has grown on me a bit. But just a bit.