Like any situation, there are good and bad points. Sometimes, the used lot of a new car dealer has THE best local selection of a particular car (the brand they sell) in their area. The flip side? A Chevy dealer wants top dollar for a used Chevy on his lot.
I was car shopping about the time Saturn looked like it was going to shut down, I could have gotten a real deal on a used car that they had recently (like that day or the day before) gotten in and not yet washed and Armor-alled to death. Bad news? It was a Pontiac....so I figured a real lose/lose situation.
I've recently posted on another topic here that I've bought my last 3 or 4 cars from a guy who works for my mechanic. Every now and then they will either buy a car wholesale, or wind up with a car a customer won't pay the money to repair...selling it to this mechanic. All of these cars have been decent runners and in some cases had a warranty.
A private seller? May give you a good price, especially if they don't know what they are selling and/or need money badly. The bad part? Next to no recourse if the car isn't what they advertised it to be.
Still, in this case, a used S-10....recommend you go private as you can get a good idea of how it was used/taken care of by meeting the current owner.