I have always likes Pioneer the best.. but they both seem to be about the same... really seems to be about the looks.... and for a girl's car the Kenwood one is a bit more giirly (with the pink lights/buttons)
Also is this going with the stock sterio or does she have an upgraded one?
Free install isn't free. It will cost you parts which will be a 15 dollar wiring harness and a 15 dollar faceplate adapter if required. So expect to pay a lil over 30 bucks for the install. All thats free is the labor. But it from crutchfield and they will give you instructions on how to do it yourself and give you all the stuff that best buy charges for in their not so free installation.