um...I'm not sure what the conclusion you are expecting me to see. Its like comparing apples and oranges. Ok answer me this What's more destuctive, a shotgun or a rifle? Too many factors play into it. Depending on the target one could me more deadly than the other. A rifle is very precise and if it doesn't hit a vital area you could be fine it hit with it. On the other hand if you are hit vitally, you'll most likely be killed instantly. With the shotgun you will undoubtedly survive at decent range. But at point blank there is no missing a vital area with a shotgun...needless to say you're fucked either way. Both weapons can kill you in different instances.
Rasengan has a spinning nature to it which creates friction and can rip away at things it comes into contact with, much like a circular power sander or as saw.
Chidori has a direct piercing nature to it which can punch holes at things it comes into contact with, much like a nailgun or riveter.
Personally I'd not like either of those things to make contact with my flesh cause it would fucking hurt like hell. The point is that both have different uses, different properties, and different users. I just don't think you can classify one as "stronger" than the other.