I always used to prefer Navionics, and probably still do for general navigation, but I've been really impressed by the C-Map Reveal charts with their almost photo-like sea floor contour mapping.
From memory Garmin kit only runs their own cartography? Could be wrong on that though, but Navionics and C-Map availability is one of the reasons I use Lowrance plotters, plus the fact that I find their user interface to be intuitive. I also like the fact that they offer a wide range of additional hardware add-ons.