edo nagato is nagato himself.. kishi just showed us that nagato himself can fight without the paths, he can regenerate his self by absorbing chakra. never in the manga kabuto stated that he did improvements on nagato. edo nagato's main advantage over alive nagato is just the regenerative aspects and unlimited chakra. other than that they have identical abilities.
this just means nagato can still fight when naruto found him in the cave but instead gave up all his remaining chakra to revive the whole village, which according to tobi requires tremendous amount of chakra.
and I've read some discussions and according to some people here, preta paths chakra absorption has its limits.. well no, this ain't DBZ kid. the ability can actually disperse the chakra or utilize the absorbed chakra by the user, which means it can absorb infinite amount of chakra.