Well you're actually going to get better MPG with the rsx. And if you get the base rsx you can run regular gasoline. With the prelude (4th or 5th gen I assume) you'll need to run premium.
If you're looking at modding, the prelude may be the better route. Parts are cheaper for older cars, and insurance is going to be less.
But seeing as this is an integra website, and i own an rsx....RSX FTW!!! lol