Not a fan of Duncan except for the color!
I have the Bizer chart on board and for my Garmin GPS/Fishfinder I have the Garmin's downloadable chart of Winnipesauke that was only $10 but it has been discontinued. So now to get a Winnipesaukee chart from Garmin you must buy either
U.S. LakeVü™ HD $149.99 or
Garmin LakeVü™ HD Ultra $199.99.
Garmin sent me this response when I inquired about the new charts.
Yes, we did some detailed surveying on Lake Winnipesaukee last year. This information has been integrated into two of our inland lake products – LakeVu HD and LakeVu HD Ultra. There will be 1’ contours for the lake in both maps. The HD Ultra map includes a few features that are not included in the standard HD map like sonar imagery, surface and side scan photos, auto guidance, etc. They are only compatible with certain device models.
They told me my 521S was compatable but I should buy their SD Card version of the maps as it is a very long and large download otherwise.
At this point I would still get the Bizer GPS over the Garmin.