Verified answer

Haha, interesting...

That's a hard one...I would say probably the Rasengan because of it's spinning force, and both of the techniques rely on the chakra control of the user, and right now Naruto can even control the nine-tails' chakra so his Rasengan has become much more powerful. Though in the start of Shippuden, Sakura's was probably more damaging.

I would say that in the beginning of shippuden they were close but now that naruto has got so much stronger rasengan probably does more damage.