They both basically have the same powers.
The difference is that in Rikudou mode you are not the host of the Juubi.
Notice the Madara and Naruto basically had the same abilities except bloodline limits. Naruto was essentially madara. But to be the juubi jin i think that it can basically be confirmed that you need the Rennin, while rikudou does not need rennin.
So Juubi Jin = Rennin + Rikudou mode. Hence why Sasuke and Naruto both had powers similar to Madara.