You can use the Premium map card in either unit ... But only one unit at a time ...
Core units cannot share mapping ... (Only Onix and Ion can share mapping) ...
All Navionics cards have the same mapping detail ...
Platinum cards have additional satellite overlay, 3d mosaic, and pictures of marinas you will never visit ...
Navionics+ cards have no mapping and you download only the lakes that you want ...
Rickie