I just bought mine this weekend and I am very pleased with the map system on it. It is very nice. You can also download a lot of other maps some are free onto the unit. I got rid of my Garmin Oregon 450 and just use my phone plus this. Even in town the street maps are pretty legit.
Cant help you on comparing with the 64. Never owned one.
I’ve run the 60csx for years. Love the interface and totally trust that device. Ran the Inreach Explorer for 10 Days this season. The map on the Explorer is smaller and not as good, but is totally usable. The ability to pair with a phone (in my case an iPhone 8 plus - with big screen) and down load all kinds of maps and map layers is way way better than the 60csx.
I still like Tracks and waypoints on the 60csx, but I’m still learning the Explorer.
All that said, I’m switching to the Inreach paired to a smart phone. I carry the Inreach for comms/emergency. There is so much overlap w Inreach vs 60csx it doesn’t make sense to carry both. I use my phone for all kinds of apps, so that’s already on me.