What device are you using? That might make a difference...(e.g. are you using one of the newer devices that can support multiple IMG files with different names?). If so, you might be satisfied with a combination of OSM, maps from here, and KMZ files. If you want something simple, you might be happier with the single Garmin $$ solution. Or you might be satisfied with just one of those free solutions. You really need to try everything for yourself...
I went through the same question that you face back a couple of years ago when I got my 78sc. I downloaded almost everything I could find, both here on this website and from other sources. For me, here in New England, I eventually decided to pay the $$ for the DVD of the Garmin 24K Topo Series, and I'm happy with my decision.
One of these days I'll make screen shots of all the different maps so you can see the difference and how I made my evaluation. But what works for me might be far different than what works for you - too many variables: coverage in your location, quality of OSM data in your area, quality of freebie (here) maps in your area, and your budget. There is no easy answer and no one-size-fits all answer.
Dave