what would be the ideal way of sealing ply for outdoor use? that's all it is really...used yacht varnish/evo-stik in the past, and as above purflex etc
GRP plywood core panels can come with what looks like emulsion slapped on the edges 'from the factory'!
never bought actual Buffalo Board but mesh floor (phenolic one side/anti slip the other) that's used in trailer/truck floors definitely don't have the same same sealing/coating on the edges as they do on the face
I put smooth outside:
The patterned side is very grippy, so it stops stuff sliding around.
Plus (and this is more a "covered trailer" thing), if you put the patterned side outside, it holds just enough water to grow green algae, so your trailer turns green.