The main thing to remeber is that alot of the big box stores you are on your own as far as warranty repairs go, If you the unit is a returnable thing then that can be done at the store if it meets the requirements. For warranty repairs you will have to seek out your local service center, if you did not buy the unit from the dealer sometimes you will not be top priority as they are servicing their own customers. (I know of a larger calgary dealer refusing all warranty work for units bought elsewhere) as warranty is normally a loss for the dealer.
When buying from a dealer they are normally the service center and while the price depending may be more or possibly less you are dealing directly with the business so if you have issues with your unit they will normally go further to make sure you are satisfied.
http://forum.calgarypuck.com/showthread.php?t=102408