Firefox has a weaker sandbox than chromium and less mature site isolation and therefore has lower security. privacy is a different story, but remember you're only as private as you are secure so Firefox is inherently not that private assuming a malicious site escapes the sandbox.

I'm fully against chrome's growing monopoly as well as Google surveillance capitalism but let's not be so dramatic with the "google mother ship" nonsense.

using chromium as a base does not equal data being sent back to Google, just like using Android as a base doesn't inherently send data back to Google.