Goku stated that he was not going all out against Metallic and even so he was winning the battle. I'd argue that Namu > Goku ( Vs Metallic ), since the former was pretty close to the latter; if Goku ( Suppressed ) was almost, almost equal to himself going all out, why bother in saying he's suppressed ? Said that, Namu would win.
Metallic 125
Son Goku ( Against Metallic ) ~ 138
Namu 145
Goku ( Full Power ) 150