I did not know the maps even existed either and looked at the Garmin website thinking you were mistaking them for the City Navigator or TOPO series. Yep, the ones you mentioned existed so it just confirms you can learn something new.
I have always used the City Navigator series and the TOPO series and the City Navigator is fine overall and is updated annually(ish). The original TOPO series has, to my knowledge never been updated but very well could be since it is so old. I "think" it is based on very old US Geological Survey maps but again not sure.
I am interested to see if others have used the ones you mentioned. I personally am torn with the OSM base map. While it is frequently the most current, sometimes the most usefully things like a bike path do not "connect" to a road so the routing does not go on the bike path since the mapping program thinks the bike path is a dead end. When I create routes in BaseCamp or RWGPS, I can just connect the open space via a "draw lines" method but if I were using to route on the bike, it would be frustrating.
I would want to know what date the Garmin Cycle Map data uses (is it from 2018 or 2023 OSM data)and more importantly how often it is updated and at what cost before buying it.
One thing to consider is how you create your routes. Do you create them at home on the computer using RWGPS, BaseCamp, or other mapping programs? Do you just route on the bike while riding? If you use say RWGPS and enjoy their proprietary RWGPS base map or the OSM series of maps, it probably would match up best with the US Cycle Map since both appear to be based on OSM Maps. If you prefer the "Map" map on RWGPS, then I would say the Navigator would match best. There are at times very subtle differences between the two maps, i.e. the "intersection" may be placed just differently enough so that the static GPS point thinks you are now in say the opposite lanes of a 4-lane divided highway to it tries to dutifully route you to that point when in reality it did not need to do so. However, this can happen also with the same map as it updates over the years. I frequently have to move a waypoint from an route created many years ago to its updated location so it routes properly.
If you end up with the Cycle series maps, let us know how it works for you.
Tailwinds, John