As a single parent, I find staying onsite and using the bus system easier. I don't have to handle a tired, cranky child and driving at the same time. I guess if I had another adult there to deal with the kid while I drove, it wouldn't be a big deal. But trying to do it all by myself is just a recipe for disaster....
I'm not a single parent, but visited frequently with just my daughter from about 18 months on. Initially, I stayed with relatives. Then the increased traffic turned a 30 minute commute into an hour commute, so I started staying nearer, but still offsite. Then the increased traffic turned a 5 minute commute into a 15-20 minute one. Once Carribean Beach opened (the first value...yes, it was a value...resort) I started staying there. Until baby #2 came along, and I hit middle age.
Since then, it's been deluxe WDW resorts all the way.
BUT...If I were staying for almost a month, I too would want to stay offsite in a villa. I know it's sacrilege, but I sometimes need a break from the magic. :lookaroun
All of our UK friends should remember that it is very unusual for most of us to be able to take a 3 week vacation. When I was working, I was entitled to 3 weeks/year, but had to jump through hoops to get them all together. My husband gets 4 weeks, but again, there is no way he could take them all at once.