I don't know the RV rental place (try 1-800 rv rent). But as far as cost comparison you will probably pay more to have a camping site, plus the cost of the rental than you would for All Stars. It would depend on the "season" that you are going and the rental rate on your RV/camper.
Then, you have to decide which place to stay out weighs the other. If you eat out every meal then the allstar food courts are convenient. If you like to save $$ by eating in alot, then the camper is the best bet. Then you have to consider what there is to do at each location: allstars, well you have your room and the pool. Fort Wilderness, you can ride your bikes, scooters, go to the campfire program at night, petting zoo, etc.
We stayed at allstars in January and my kids hated it so we went back to FW in May and they were all happy.