In the case of selling your car yourself versus trading it in, the ultimate factor is how much you value your time. Depending on the car, getting top dollar on the used market can be a monumental task. Dealing with tire kickers and lowballers can burn up your time. Moreover, preparing your car for sale can be quite time-consuming as well.
Another thing to take into consideration when selling your car yourself is the fact that the prep for sale can incur costs in itself. For one, a great way to help your car sell faster is to get it serviced. Basic things like an oil change, new brake pads, etc., can help draw buyers in, but they are going to cost you money. Getting a professional detail or doing it in your garage and a nice set of photos to go with your ad are also common ways to up your curb appeal. Unless you’re doing all of this yourself, though, the cost is going to stack up rather quickly.
There is, of course, the option to sell your car as it sits. A quick vacuum for a couple of bucks and some decent photos can go a long way for cheap. However, without presenting it to be as perfect as possible, getting top dollar can be a bit of a long shot. In some cases, though, selling it “as-is” may still net you more than the dealership is willing to offer you.