1st of all, ML and Nav are 2 seperate option, you can buy one without the other. If you are from Fall River MA, than most of the GS will have the Nav but not the ML system. My best advice is to go listen to them both back to back. You cant compare it to the Bose system, because the Bose system, much like ML system are very different in different cars. I listen to the ML system and the Lexus system in the GS back to back at the dealer for 30 minutes. The ML was a tad better, but I could not justify the extra $2000. To me, the OEM system is pretty good for a standard radio. Again go test drive and test listen and then decide :) Make sure you bring a good CD or DVD music if you have it.