Interesting thread. Despite living in the dampest area (sea-level drained marsh land) in what must be one of the dampest countries in the world - I run most of my hives successfully with sealed, insulated tops and open-mesh bottoms.
I still have one or two hives with solid bottom-boards which do become very wet inside at this time of year. Inserting popsicle sticks between the brood box and bottom board to create a 2mm gap, or inserting cut-up credit cards between brood box and crown board (inner cover) to create a 1mm gap - taking either of these steps is solving this problem until such time as I can get around to making mesh floors for those remaining boxes.
So - in my experience - either top or bottom ventilation will work ok. My own preference is for bottom ventilation, as it seems to make the most sense - but - I'd suggest you try both methods and see which works best for your own hives, and at your particular location. Putting some kind of skirt under the Open Mesh Floor is always a good move, or a substantial windbreak around the hives.
'best
LJ