I am both and I can say the great demon lords kinda win.
Muzan is smart and strong yes, a formidable opponent even for even extremely skilled humans, but the seven great demon lords are just stronger and might be smarter.
Muzan mainly fights humans (granted humans who preform superhuman feats) and is used to it but the demon lords fight powerful monsters and win 99% of the time (the one time being when they fought the main characters), they almost brought to ruin the digital world by themselves and there are some pretty tough digimon yet they lost to these seven in fact they were simply sealed in egg form because they just couldn't be beaten even then it was temporary.
They even just straight up subvert anubismons reincarnation cycle as the data of whoever they kill becomes a part of them, in fact one of them (lilithmon) just has an ability that decays whatever she slashes with her right hand
