Last month, I had a car reserved at the Dolphin, to return it three days later at Tampa Intnl. But, I found that I had to go to MCO to meet my dd, and then drive to Tampa. While checking rental prices at MCO I found that it was actually cheaper for me to have my towncar company drive me back to MCO and then rent the car there, rather than rent at the Dolphin. I can't remember what the exact difference was but it had to be at least $50 less since that's what the towncar company charged me, and I didn't have to pay to park as I would have had to do if I rented at the Dolphin and drove to MCO before heading to Tampa.
I think you really have to just run all the different scenarios and then make a call as to what is going to work better, and more cheaply, for you.