There are a lot of small vents( on the Kask) covered with fine screen mesh, but I think it may be too fine, something more like the Vertex vents will be more inline I would think 
Also with some independent- anterior- whacking of the cranium; I think the vertex might fair a bit better with a major sideways hit with some big wood.
But the Kask seems like it would take a direct hit on the top of the head better...it all boils down to whatever you feel more comfortable in and whatever you believe in! they are both great helmets, the best out there, so you can't go wrong with either; or do what I did, buy one of each!
Also with some independent- anterior- whacking of the cranium; I think the vertex might fair a bit better with a major sideways hit with some big wood.
But the Kask seems like it would take a direct hit on the top of the head better...it all boils down to whatever you feel more comfortable in and whatever you believe in! they are both great helmets, the best out there, so you can't go wrong with either; or do what I did, buy one of each!