The main difference, skingg, is the fact that the DC5 JDM (not the US poser!) is a car tuned for the track, as all Type R's are and an RX-8 is tuned for the street, so it's somewhat of a Grand Tourer. I see you're a BMI fan. Watch "Rotary Reborn" and you'll see what I mean.
Integra Type R's (DC2 or DC5) are such great handling cars that they can easily hold they're own against any car with similar power outputs, be it FR or 4WD.
Remember though, this is only a game and once you start modifying these cars anything you've seen or heard in the real world can be thrown out the window.
If you're comparing these cars in stock form I suggest using N2 tyres on the RX-8 and N3 tyres on the DC5. That, in my opinion, would best simulate their real world counterparts. Stock Type-R's have such grippy tyres it's almost impossible to get any understeer and when driven with the wrong set of tyres they feel a little sloppy.
My friend has a DC2 and he bought it 2nd hand with lower grade tyres than stock and it made me wonder what was so great about a DC2 ITR. It's important to use the right tyres on a car like this as it has been tested to death by Honda to match the car's overall balance.
I'd guess, as I haven't driven one, that the RX-8 would best suit N2's for it's more a Grand Touring Sportscar rather than outright track based Race car. Remember, this is for stock cars. If modifying you might even want to use softer tyres on the DC5 than the RX-8.
RXGem
Rotary AND VVT enthusiast