Lol dude this is mostly conjecture, not even gonna touch the hypotheticals.
But on to manga facts. Its stated very clearly that Kabuto improved on Oro's Edo Tensei and that he surpassed Oro. Kabuto and Oro studied with each other extensively so idk how you figure anybody copied anybody. But in any case Kabuto showed far more ability with Edo Tensei.
I know that Kabuto absorbed Oro but he also found Ryucci Cave himself and trained under the great snake sage. Orochimaru could never really handle senjutsu so I dont think Kabutos sage mode is because of him. I think be mostly absorbed Orochimarus abilities.
And when did Edo Hashi "beat" Edo Madara? As soon as Madara "got serious" he wrecked Hashi in like 2 moves and stole his senjutsu.
It's conjecture grounded in facts and based on reasonable logic drawn from context. Pain went at Naruto hard from the beginning with all Six Paths and used much more devastating jutsu. He went hard because he knew Naruto was a Sage. Against Jiraiya he was clearly too caught up in his own hype and was toying with him. He didn't get serious until Ma and Pa caught 3 of his bodies with Frog Song. Pain had no intention of allowing Naruto the same leeway.
Kabuto
claimed to have surpassed Orochimaru. He may very well have considering he managed to pull off Sage Mode, something Orochimaru could not. However, on the matter of Edo Tensei specifically, Kabuto was depended on Orochimaru's chakra to bolster his control.
Kabuto summoned more people with Edo Tensei. That isn't conclusive evidence he was better at it. If you're going make that claim based on quantity, I'll simply point to Edo Hashi, Edo Tobirama, Edo Hiruzen and Edo Minato - all of whom vastly stronger and more impressive, i.e. of better quality, than all but Edo Madara (who Edo Hashi whooped) and who, save for Hashi, Orochimaru could control.
Orochimaru used senjutsu chakra for his Cursed Seals which are a form of senjutsu. He simply couldn't master Sage Mode because his body wasn't strong enough. Kabuto likely wouldn't have been able to either if not for infusing DNA of the Sound Five and Orochimaru into his own.
Edo Hashi beat Edo Madara right before Black Zetsu forced Obito to use Rinne Tensei and revive Madara, thus restoring him to his true prime. Before that, Edo Hashi and Mads were going at it with their full strength and Hashi beat him and was close to sealing him.