I've always stayed offsite and NEVER will again...
As a child, I was at Disney maybe 3/4 times. All of which were offsite. Last year DH, DD and myself were asked to go for 2 weeks with 10 other family members, again, offsite.
I could see all the action at some of the resorts while riding the monorail. It looked so fun to say onsite. I LOVE being in the center of the action. Our next trip will just be the 3 of us (DH, DD and myself) and I VOW to NEVER stay offsite again. I'll spend the extra $$ to have those memories.
I don't care what the cost and if I can't afford a moderate (for whatever reason), then I'll go to a value. Since I always plan the next trip so far ahead (actually, as soon as I return), there is no reason why I can't afford to budget for a moderate. I just budget all my expenses, divide it by the months/weeks, and keep saving...Income tax really comes in handy...
I'm so bad that even when I stay at Knoebels, I HAVE to stay in the campground. I love being right across the street and hearing all the action.
It's all a matter of personal pref.