imho
As far as orgs go, there is only "GUE" and "Others", meaning that the name of the org is irrelevant unless its GUE. So if you want to go the way of choosing org that carries weight and then instructor - GUE is the only way that makes sense
Now, the only real advantage of GUE is that you are 99% guaranteed to get a great course regardless of who is your instructor (which is why you pay the premium). If you don’t want to pay extra and instead go with "Others" (which is what I did), its 100% about who is your instructor, and its 100% on you to do your research about the person.
SB is great for choosing US and Mexico instructors simply because there are way more reviews about them here; not so much for EU. There is "French SB"
Plongeur.com - Le site de la plongée sous marine and maybe you will find more info there. I don't know how active that forum is, if at all. That said, there are some EU cave divers here and it might be best to dig thru different threads to find them and to reach out directly