well shinten is only better if you crit 2 time on the 3.... if not a crit midare is far more efficient. depending of your direct hit, your midare (kaiten) hit between 16-18k when shinten hit around 5-7k on the paper is better, but...you need to get the direct hit on 3 attack. then *shrugs* both are working.
plus if shinten was this strong, it will be a nerfed already.