I've not studied the differences between the two the way Doug has, but it would appear that one major difference between the two is ACR's 406 Link Service. Also ACR does have a spotless record in this area. As I do not plan on using the check-in capabilities on my PLB (I have a Spot 2 I received as a gift that I use for that), I'm going to stick with the Fast Find 210 at least until its battery expiration. Although it may seem silly carrying two devices, I just do not like using the battery capacity on the life-saver device for non-emergency traffic and if PLB standards remain that a non-user replaceable battery is standard, I'm not likely to change my mind.