Depends how many bikes you have and what you want to use it for. I went through the same dilemma but already had a cross bike and wheels etc from that, so in the end went for the cross check. It is now my ‘road’ bike and used mostly on road, but also farm tracks and gravel roads. I have it set up with midge drops and It works nicely with a variety of tyres including 1.8 29r tyres, but that gives serious toe overlap!
I am lucky enough to also have an MTB, but I think if I had a bit more cash and / or could have only 1 bike, then I would now choose a KM but with 2 set of wheels.
I think the decision would really be around what the majority of riding done on it will be, and if you want flat or drop bars. If mostly offroad then KM, if gravel and road then cross check. If flat bar then KM as longer top tube.
I should add though that I love my cross check. Even though it weighs a ton it rides really nicely and feels like it can handle a lot more than it does / should