i can totally see the chidori and rasengan taking about the same amount of time to charge....at least not enough of a difference for it to be a big factor anyway.
for whoever's saying sasuke's target has to be stationary.....no
the whole idea of the chidori is that it is supposed to be coupled with the sharingan, so the user CAN move while charging in order to accurately hit the target while dodging any counters.
and btw, it is true that sasuke DOES need more distance to cover for the chidori than naruto needs for the rasengan. This is why kakashi had sasuke build up his speed.