We are trying to give advice to one of our junior members. Using a term such as "misinformed" don't lead to a helpful discussion- and Dave is very experienced in speaker building and well informed. That doesn't mean that his opinion cannot be politely challenged.
I don't entirely agree with Dave, and think that describing mdf as a 'poor" material for speaker cabinets, especially in the case of a pair of AV-1 speakers. Actually, I've built very similar designs with both Danny's woofers and tweeters out of mdf and high density ply, and like the ply slightly better. However, around here Baltic Birch is pushing $100/sheet and mdf is around $25. Excellent small cabinets can be made from either when thoroughly braced. Remember our goal of helping advise a fellow member to successfully build his project. Regardless of preference, the pieces are already cut out of mdf, and it would be silly to throw them out in favor of ply.