Michael Brockers is putting the argument to bed ... the Rams star clearly believes L.A. won the QB trade with Detroit -- telling TMZ Sports Matt Stafford is just better than Jared Goff.

"Is it a level up?" Brockers said when asked if Stafford was an upgrade over Goff. "In my heart, deeply, just understanding what [Stafford] brings, it's a level up [over Goff]."

"It's a level up."

The Rams gave up Goff and a treasure chest of draft picks -- including two future 1st-rounders -- to get Stafford out of Detroit ... and many felt L.A. was fleeced in the deal.