Which car would you guys choose if you werent allowed to mod it anymore and had to leave it as is.   A front wheel drive 300whp car or a rear wheel drive 220hp car  

you already know my answer.
seeing as how the FF will only get about 250 of its HP to the ground and have trouble acutally turning, RWD without a doubt.

which 2 cars in particular are we talking about though, or is it hypothetical? like once of those "what supercar would you buy?" as if anyone here the cash for one.  

I'd go with rwd. There's only so much you can do with a car that's front wheel drive. I know because I own one. But it's good for daily driving. Rates lower on the fun-o-meter though. Did I just say fun-o-meter?