I can't speak specifically about the PG Academic Showcase because my 2016 did not attend but if it's like the PG showcases he did attend there would be a marked difference between it and the HF showcase. First, as Backstop pointed out, you'll know what schools will be in attendance at HF where you won't know who will attend the PG event until or if you see them there. Second, the schools will be sometimes visible, sometimes not but at arms length. At HF the player (and parents) will be right with the coaches as they are everywhere - on fields, in seats, walking around, etc. You will get a booklet with the coaches in attendance and their picture. Your player will be able to find them and speak to them. There is a cost for this yes, and it's not cheap. But, it's really not that much more expensive than a PG event in the grand scheme of things. I could not find the cost of the Academic Showcase online but the cost is similar to the NE event that my 2016 attended we're talking a drop in the bucket when compared to what I spent over the years - about the cost of one high end composite bat.
Depending on where you are at in the recruiting process and what level you expect your son to play it may not make sense to guess on who will attend an event. At some point you'll need to know who will be there and be able to target them via communication (email, phone, smoke signals) to get them to your game during the event. I may be wrong but I just don't think you can do that at a PG showcase (and I'm guessing someone will tell me I'm wrong). Either way it will come down to how the player performs on the field and what their grades/tests scores are like but I would not go into an event that costs that much without more information to work with. Just my opinion.