Easier maybe, especially with the shuttle services. But I'm not so sure about cheaper. We usually drive but on occasions we either flew or thought about flying, I would price cars both upon arrival/departure from MCO, and renting at WDW the day after arrival and returning the car the day before heading back home. In every occasion, every rental company, every car type, renting for X days from MCO was cheaper than renting for "X-2" days at WDW. I suspect it's because there are so many more cars at the airport to choose from, the volume warrants competition. I last checked prices a few months ago - we've since decided to AutoTrain down and drive back - but that discrepancy in prices still was there.
EDIT: Aaaaaand here's where I contradict myself because for chucks and giggles I checked prices again from Alamo (without applying any discount coupons or codes). I put in dates from MCO for the duration of my upcoming stay, and then the day after arrival/before departure from the WDW Car Care Center. The Car Care Center price is significantly cheaper. I did change my dates from the last time I checked. I don't know if it's the change of dates that significantly affected the price, or if they dropped prices based on some kind of current lack of demand but for whatever reason it upends what I wrote earlier. Probably best to always check both ways unless you need a car for your entire length of stay.