Some great posts already here.
I think the comparison between PG and PBR has some differing values based on your son's talent and school targets as well as some geography. If your son is seeking a low D1/D2/D3/JUCO, then PBR may be more advantageous as it seems to have a more regional following. If your son is a top-500ish nationally ranked prospect, then PG is probably worth the added cost.
Worth reiterating... don't go until your son has measurables desired by your target schools. Otherwise, as anotherparent said earlier, your son will constantly be looking to update those older, less impressive numbers (and costing more money to register and travel). And do NOT go to any showcases if your son is playing through an injury or soreness that would impact performance and/or measurables.
My son ended up at a low/mid-D1 and had by his rising senior summer the measures typical of players at such schools. While there is *some* projection involved in showcase evals, it's probably less than one might think. For example, while my son had developed desirable measurables by his rising senior summer, he was too projectable in his rising soph and junior summers to draw legit recruiting interest early.
Also, if your targets are high academic schools, then go beyond PG and PBR to look at Showball and Headfirst showcases. Probably not worth doing though any earlier than the rising junior summer, and as a pitcher, maybe even the rising senior summer.