agreed with the above, if your going to go with one go tomini, they seem to have a more mild personality. I have one of each and unfortunately had the kole first and it took about a week+ of chasing and tail whipping before they calmed down, luckily no cuts or dmg during the adjustment period. Both tangs seem to be just as good at algae grazing as each other, tomini might pick a bit more.
Also My Kole used to be mean to my lawnmower blenny, probably due to them both being algae scavengers, Blenny still steers clear of him.