Here are my thoughts on the Sync3 vs Sync4 vs Google-based systems:
-Sync3: It really isn't a horrible system, it can be good like in my Raptor, where it isn't horrible. The Sync3 is just so horribly designed in the Explorer's Vertical screen, and is an old system too, so it's slow
-Sync4: I am a huge fan of Sync4. Wireless Carplay/Android Auto are notable upgrades compared to Sync3. It is a lot faster, and has cool split screen options
-Google-Based (I have no experience with this system so I am completely speculational): not that much different then Google-based, cheaper for Ford to develop, and special connections
None require any subscription to operate, but all the above need a subscription to use the built-in navigation or SiriusXM.