Proximity to the parks, plus the convenience of not having to drive, and getting dropped off near the park entrance. We normally always stay on property. However, a month ago, we completed our first off-site stay. Only reason being that at one of our kid's school fund-raisers, we had won the use of condo in Kissimmee for a week. What a hassle to drive to the parks, pay the $22 for parking (many places I would opt for preferred parking as its usually 35-50% more than general parking, but at WDW it's more than double), get directed to park in a specific spot even though there are much better/closer spots available (though I understand why they do it,), then tram/walk in the heat to the park entrance. We missed just hopping on Disney Transportation from/back to our resort badly the entire time. Combine that with lousy FP+ availability at 30 days, no DME when getting off plane so having to retrieve luggage and then get rental car (RAC didn't mater this time since we were getting on the Fantasy at the end of our week) and we basically came to the conclusion of "Never again" when it comes to staying off-site.