They are very superficially similar, and very different at the same time. They both contain two man sparring with designated target zones. The Fencing guys where a face mask to protect the face, but are mostly armorless otherwise. The kendo folks where somewhat more armor. The fencing guys tend to thrust a lot, the kendo guys do a lot more cutting.
What you are asking is a lot like comparing basketball to soccer. They have a little bit in common, like balls, nets players, a general goal of getting the ball in the net, but otherwise they are VERY different.
Breaking down bad habits,
and building new ones.