I can see why you went with MDF for your former. Like you said it is easy to shape but otherwise not a good material for beating on or for using where moisture is present. There is an exterior grade MDF which might work for the moisture problem but would still fall apart after several beatings. Marine ply is pricey. Any cabinet grade ply should work as long as there's little to no voids on the edges. Be interesting to see what they use in the course you sign up for.
