Since I can't say for sure BB is acoustically better for cabinets, it really comes down to how you are going
to finish the cabinet. BB is the best choice if you are veneering because the veneer adheres much better
to the edges than it does with MDF. But if you are painting your speaker use MDF, it is much easier to paint.
Both BB and MDF are flat and cut beautifully, but I hate MDF dust. It will be everywhere in your shop, in your cabinets,
in drawers, just everywhere. All that dust and I always veneer speakers is why I use BB.
I also made the baffle 1-1/2" the entire length of the baffle. Don't know why the baffle in the plans were designed that way,
but a full length thick baffle would certainly be much more rigid and stronger structurally, especially if using MDF.