Chidori is to be used as an assasintioan jutsu? It gives off a sound strong enough to wake e dead person, it flashes enough to send signals around the globe and it is supposed to be used for assasination? And here i thought assasination should be done as stealthy as possible with no one noticing.

The Rasengan is better, you can use it in diffrent situations and tactics. Chidori works one way, run fast and dodge your enemy while trying to pierce him through the chest.