It is a convenience vs value trade off. Selling to the dealership will get you less than market rate (since the dealership will ostensibly turn around and sell it at market rate.) You haggle at most once. The couple of cars I have sold to Carmax usually got me with in a few hundred of KBB.com's price so I sold to them.

Private sell feels like running your own private dealership for a few weeks. People call and want to come see it, take test drives and haggle. It has usually taken 5-6 inquiries for me to sell privately.

note: N for both carmax and private sell = 2 so your milage may vary.

Do you think there is a certain market that does better in private sales (for example: cars under 10K & collector cars)?

My experience is that there is a middle range of cars where consumers would rather pay a little extra to make a trustworthy purchase from a dealership (if those two words can be used together!).

I can't say I have ever seen a classic car sitting on a dealership lot. My suspicion is they are considered too hard to sell so the dealership would take them to auction where specialty dealers or collectors pick them up. So yeah I guess most classic cars get around by private sell. For really cheap cars I think those typically go to unaffiliated dealerships, buy here pay here type of places or private sells.

I'm doing this right now. I just got a quote from a local dealer. I have a 2011 Audi A4. The dealer offered $23,500 and will go to $24,000. If I sell privately, I can probably get $27,000 maybe $28,000. But, it will take weeks and I have to be very careful of scammers, etc. It's a tough call and I haven't decided what to do yet.

FYI - I'm going to take the dealer's upgraded offer of $24K.