I've built numerous ramps with most types of surfacing.
I have also worked building both wood and concrete skateparks
Metal will be the most expensive. And gets way to hot
Skate light is the best. But also expensive
Check out this stuff.
http://gatorskinsramps.com it's like skatelight.
Lasts forever, I have a ramp that's almost 7 years old with it, in Canada where we have snow and heavy rain 6 months of the year.
It is never tarped. We have had to do repairs to the underlayer of plywood, but the top is still beauty.
Masonite will fall apart with any moisture.
Good one side ply or birch ply, work well. It will last way longer than Masonite but will eventually chip and fall apart.
It should be painted or treated with some sort of weather treatment. And if you can caulk the seams it also helps
(Like Thompsons water seal),
Don't listen to tracer.