The rx-8 is pretty much crap but should have more horsepower than a celica.
Gas mileage...celica; rotary engines don't get good gas mileage.
Repair...celica; very few mechanics are able to work on rotaries (regardless of what they say)...
Faster/performs better...rx8 when it's not in the shop
Maybe you should look at some other cars like a 350z or chevy cobalt ss supercharged they're better built than the rx8. I still like the way rx8s look but they're just not very good cars especially when a)used and b)you can't do the work yourself.