I just went through the same debate for myself. On monday I ordered a MS660. I've alwayse hand and used Jonsered/Husqvarna on my saws but our local Jonsered dealer doesn't handle anything over 71cc, there isn't much for Husky dealers. The John Deere dealer where I spend a lot of time and do business is also a larg and well stocked Stihl dealer, and is verry good to deal with. The pricing on the saw was also more atractive than others and other dealers. Also a Stihl distributer is only 60 miles away and a lot of things come next day.
I orederd one with the full wrap handle to start with, regular handles are cheap on ebay, but full wrap handles are harder to come by.
I've also got other Stihl bars and can run the adapter on my Jonsered, I can keep all my chains of the same gauge/pitch. Just a few reasons why I went with the Stihl, could have just as well been the Husky, not likely I'll need much of a dealer for either, other than initial purchase.