Rent car, Shuttle, or Cab to Universal from Disney?

[marriedmarylander]

We plan to go to Universal/IOA for a day (maybe just one depending on time). If we rent a car , shoudl we try to return it the same day later that night or the next day? Doing it the same night is cheaper but I'm afraid we might be in a rush. The thing is the next day we have to be somewhere at 8AM so we couldn't really return the car and would have to keep it longer , thus paying more money (Probably $40-$60 depending on car company, if we have a discount). Factor in parking and gas as well... and we are paying almost as much as it would to take a Mears Shuttle ($70 roundtrip right?). Although it may be nice to have a car the next morning to go to our Disney Park and not have to deal with the bus.
I'd like to try to book a car ahead of time so I can use a discount and make sure they have an economy car (I'm not paying more for a bigger car).

 

[robvia]

I tell everyone to rent the car.
Yes, you pay for gas and parking, but you can go where you want, when you want. Plus you can visit the grocery store and fill a styrophome cooler with drinks. Check out my Orlando pages for directions everywhere.
http://www.nogodforme.com/orlando2004.htm

My rental car becomes my home as I visit the parks. I bring extra cloths, the cooler, and then have a drink as I'm walking to the park.