first of all, raikiri is a completly seperate jutsu from chidori, Kakashi created it because he couldn't combine his lightning element with rasengan. secondly, kakashi is still stronger then sasuke, he has more experience and more elements at his disposal, plus kakashi's sharigan is always active so he'd be using it from the beginning of the fight to the end. third, there is no proof that sasuke has tsukyomi, we havn't seen him try it and so far it seems that each different MS has different properties and attacks. and i'm saying this because its my opinion not because of my preferences for characters.