Nagato was an uchiha and so he naturally has a strong life force and large chakra amount. Nagato, even though it has nothing to do with not being an uzamaki, probably didnt have the life force to handle both, also we have to keep in mind that nagato had them since he was a child, so his body was more able to adapt to them, while obito had it only from the time with konan.
Orochimaru wasnt weaker. Hashirama DNA helps people gain control over various jutsu, Danzo used hashi dna to shorten the time for KA, and to be able to implant sharingan in his hands, madara and obito used it to gain better control over the juubi, orochimaru himself used it to strengthen his control over the Edos that he knew he could not control if they were brought back at 100% of there original strength. I dont believe madara made 100,000 zetzu clones, I believe those clones were the remnants from the first time IT was casted. Madara probably just implanted them with hashirama dna, becuase the fact that the zetzu contained kaguyas will, and was able to take control of black zetzu. If they were his original beings then I doubt it would have went that way. But I already know the counter argument is, "kaguyas will was in the gedo duh, her zetzu will be stronger, blah, blah".
lol 
