Time! That is your biggest consideration. You can sell anything privately, but how much time are you willing to wait for someone to come along. They might show up at your door 15 minutes after you make something available for sale, and it may take 15 years.
With a dealer, you know they will take it, but at what cost (or loss) to you.
So the balance is time. One is certain (right now) but a lower sale price to move them. The other is uncertain time, but may result in a higher sale price in the end. And one thing you have to remember, time is not your friend. Every day you own an RV or a vehicle, every day it looses value. So there will come a time, if not sold immediately, any decent resale value may not be so "decent" any more.
It's a fine balance. Your willingness to play the wait game will drive your decision.