Kelly's won't be a good representation of true value because it is bank owned, so their values will generally be higher.
Edmunds will be more accurate as to what a buyer would actually pay for your vehicle. From what I understand, they tie their pricing to actual closed sales and not listings or failed sales.
If you will be dealing with a dealership, then if it is a trade-in, then they will generally be willing to pay you what they would pay to buy a similar vehicle at auction. If your particular vehicle is rare at auction, they may be willing to pay more just to get one of them. Your best bet for auction related information Manheim.
If you will be selling your vehicle to a dealer for cash (not as a trade-in), expect them to knock even more off an at-auction price.
Generally, at least what I have found to be true with luxury vehicles, is you will find any offer from a dealer to be well below what you hoped for even on the low end of the Edmunds scale and certainly lower than the lowest Kelly's.
Current: 2015 i3 REx | Giga | Ionic Silver Metallic
2013 550i xDrive M Sport DHP | Jet Black | Venetian Beige | Dark Red Sycamore
2008 535xi Sport | Jet Black | Cream Beige | Burl Wood