I considered both cars (and a bunch of others) before deciding on the TSX. The RX-8 is a great car, but I found there were a few too many practical limitations for me as a daily driver.
- I wanted auto as well (stop-n-go commute), but the RX-8 auto is 4 speed which makes the paddle shifters kinda useless. I'd (personally) feel bad getting the RX in auto anyway.
- Despite the suicide doors, there isn't all that much room in the back and the seats don't fold.
- A loaded RX-8 in Canada is $10k (list) and the dealers won't discount, whereas I got about $2k off the TSX, making a $12k difference, which is huge.
- 3 month wait, unless I wanted one off the lot which came with lots of useless options.
- Poor mileage (I have a 80km/day commute).
Of course, the RX-8 has all that sex appeal, good looks, rarity and it's a true sports car and not sports-lux sedan. I think if practicality isn't an issue for you, then go for the RX-8.