Probably cheaper, but not as fun. I think I rented an econo car for about $125-150 for 4 days through Orbitz. On top of that I got insurance for the whole trip for about $90. And then when I actually picked up the car, they decided to add an extra $250 because of my age (which was stated could happen on Orbitz's website). So, overall I spent about $500 on an econo car I barely drove 100 miles in. That's almost like throwing money away.
Well, a 1 week (maybe more) long vacation in the Dart driving approximately 5000 miles can't be too bad. It sure would be memorable as I could make some stops along the way. It would probably cost $200-300 more in gas, but at least I'll actually have a car to drive down Woodward and enjoy. The only issue I'd have is if something went wrong or broke along the way.