Hi, we did this last year. We weren't hiring a car, so faced the same dilemma.
We used a "private" transfer/taxi sort of thing. He was a lovely man who had retired, and now only does airport transfers. We found his details on the sanford airport website - they have a rather long list of airport transfer companies and people. So, I'd check that out first.
His car was lovely, and he spoke to us a lot about Orlando during the journey, recommending certain things and so on. He met us at the airport and dropped us right outside our hotel on IDrive.
I'd really recommend Ed, and I'll find his details for you later. Hope that helps.