I'm not particularly a fan of KB teaching naruto how to control his tailed beast.
It also doesn't appear to be a learned skill but more of a bloodlimit or trait they simply have.
The only ones known to fully control beasts are 3tails and 8tails, to the full amount of tails as it were.
The 3rd tail host didn't appear to be trained for it or anything, he just could.
It also seems KB didn't need to train either, maybe its a personality thing????
KB and his octo friend appear to be very similar.
For the reasons above I personally think Kisame is going to win, and own KB. And then everything will be up to Naruto to save the day as he'll be the last one needed.
I don't see Kisame losing personally, while the fight sucked and sasuke essentially died 3 times (got his ass saved by karin, suigetsu and juugo three times by fatal blows) but KB still had some trouble when it came to amaterasu and such like.
While Kisame has no sharingan, he appears to be able to dodge damn fast stuff, like the raiton pencil attack.
He is simply stronger than KB for sure, given Gai couldn't match his strength until he opened 7 gates, and kisame was only 30% there.
He also has loads of moves we simply haven't seen.
Also samehada is definitely going to change, definitely a "shidai" at the moment, bankai will come soon

and own KB.