What is the difference between "Contacts Sync" & "Contacts Sync Pro"?

Contacts Sync and Contacts Sync Pro are functionally equivalent.  The only difference is that Contacts Sync is a free app with paid upgrades, while Contacts Sync Pro is a paid app that is fully upgraded.

Contacts Sync is available at the App Store at:
https://apps.apple.com/us/app/contacts-sync-google-more/id454390333

Contacts Sync Pro is available at the App Store at:
https://apps.apple.com/us/app/contacts-sync-pro/id686378579