Stax for me. A very long time back Joe Hubbard recommended a Motown compilation " Chartbusters vol 3 or 5 ?" As I really only listened to punk this was a departure for me.
Boy I'm glad I bought it as I started looking for Soul and R&B in the record shops,which of course lead me to Stax. Mavis Staple,Booker T,Otis,Issac Hayes ! Oh the talent is
astonding.
While Motown is still great as is Fame/Muscle Shoals, Stax and it's close ties to the civil rights movement give it the edge for me.
Just thankful we've got all 3.