Ply is lighter and stronger than MDF. With very large and heavy drivers MDF does not hold up well. I just find ply to be the better material. For you, MDF is probably the better choice.I have a plywood cutting jig I made that works well. Click the attached link. You will have to click on each image icon to view the photos if you are not registered at that site.
I use aliphatic wood glue with bats and screws, screwed from the inside so they don't show. I cover the ply edges with "birch tape". Then sand, stain, and apply several coats of hand rubbed tung oil.