Any private sale is going to hinge upon price and convenience to see the rig. If you are near major population areas, private sales are easier than if you live 50 miles out in the sticks. Just be aware you are likely to waste vast amounts of time dealing with lookie Loos and people who have no ability to buy.
Another factor is going to be whether or not your rig is going to be financeable. If it is older than about 7 years or has higher mileage, your buying pool is going to be greatly reduced.
My advice is to be very sure you are properly priced. Don't put a penny of value onto anything you have added or changed on your rig. Nobody is going to care that you spent an extra $2000.00 on custom paint graphics or spent $5000 for the 50 inch Plasma TV upgrade from the factory. They know the paint adds no value and a better 50 inch TV can be bought for less than $500. The fact is almost all factory options have little to no value at all when it comes to resale.
There is a very limited number of buyers for $100,000+ used RVs and you don't want to miss one who would otherwise be interested in your coach because you initially set the price unrealistically high, hoping that someone will bite. Most people who can afford to buy a $100,000 plus RV didn't get into that position by paying a premium price for their possessions.
I may be in the minority, but I prefer to buy from a reputable dealer. That way if something is truly out of whack (say major structural damage was not disclosed, or the rig was represented as having a Cummins 600 and I discover the badging has all been changed and the engine is actually ISL 400), I have someone with assets to go after.