Basically, yes.
Mapsource is no longer being updated, and 6.16.3 is the last release to the best of my knowledge.
BaseCamp also lets you look at maps which you have bought on SD cards and exist only as IMG files within the device, which Mapsource will not.
Personally, I find basecamp counter-intuitave, and I can't find any of the features I require. So I continue to use Mapsource.