It's confirmed, Obito will lose to a rasengan

[Honord Sage]

That was a Sage Rasengan use here, Natural Energy not your normal Rasengan. The Second Hokage senses detected it and He even said Naruto dose a brain,He was surprise that Naruto came to right conclusion base on the evidence presented to Him.

 

[iNotorious]

All the fights of naruto ends up with a rasengan, or a new type of rasengan such as the movies one.