You can't prove anything once and for all. Comics rarely work that way.
MM does have some portrayals where he is Superman's physical equal, but they are outnumbered by ones where he is not. And he has no portrayals where he is actually stronger.
But on the other hand, it can be argued that Supergirl had Loeb force when she wrecked him, but it doesn't make her any stronger than J'onn as he was able to draw blood from her. The funny thing is that weaker white martians have been able to completely stomp Superman and J'onn on the other hand been has shown to speed blitz them.
And considering MMH easily overpowered Ultraman who by the way has the exact same power set and feats as superman doesn't make him not consistently more physically powerful?
Martian Manhunter is obviously more powerful given his vast variety of powers and their utilities.
But is he stronger though? Personally, i don't think so, we already have another Superman's equal and that's Captain Marvel/Black Adam, and every time MMH fights Cap or Adam in pure physical battle, he gets whooped hard. In Underworld Unleashed Cap (at 50% of his power, since Mary was also powered up) nearly killed MMH, in WW3 Adam (less at 50% of his power, since he gave much of his power to Isis which was contained in amulet, and he didn't return that portion of his power back during WW3, as the amulet was shattered and those parts were hidden) pretty much 2-3 shotted MMH.
In short MMH, while can claim to be strong as Superman, when actually facing Superman-level strength, he doesn't perform so well.
Versatility is overrated. Comics aren't realistic. I think Superman is both decisively stronger, and at the least significantly more powerful on the whole, in the comics world.
Having more powers and being more powerful are often not the same thing. There is the Fernus aspect to consider, but I don't think you can really call that J'onn.
Superman has more power, imo. It's just spread across fewer outlets than J'onn's power is.
Versatility realistically adds more power: if you give Superman another power, while granting him only the same amount of total power, he is in one sense more powerful, and yet not in another. Sometimes writers value versatility, but on the whole, they do not value it nearly as much as it realistically should be.