Another vote for kepubs here
The ability to zoom images is helpful, as is the fast page turn, occasionally. I was surprised to see it said that the difference in speed is unnoticeable, because that was not my experience when I tested it with an epub and kepub version of the same book. Admittedly, there aren't that many occasions when the VERY rapid page turning is needed, but it's one of those "hey, that's handy" kind of things when the situation does arise.
Ultimately, of course, it's whatever works best for you and the intended end users, but I will say that describing kepubs as "disastrous and to be avoided" is a touch hyperbolic. The great thing is that trying both will inflict no harm on you or the devices in question, and will lead you to the only opinion that matters here. Yours.