Naruto because rinnegan consume a lot of chakra, not to mention I believe it needs a host with strong body like the senjus/uzumaki.
Since Naruto is the stronger one out of the two right now, he would be the stronger one if both were granted the Rin'negan. His Chakra reserves would also most likely allow him to use it to a greater extent that Sasuke, similar to how Nagato's Chakra Reserves allowed him to use the Rin'negan so well.