It really depends on which one is important. Since you and many others believe the leech is good, the bond skill of naruto's won't make a difference in your opinion. However, if you care about damage and using the mystery almost every round, kcm naruto would be the better choice since he'll get more damage and interrupt. Since some might not know this, kcm naruto has a higher chance to lower its mystery countdown than 6p naruto. 6p naruto won't be able to all the time and if it happens that 6p does then the difference between you and your opponent's combo rate is too high.