I have been told that people with kinky hair dislike anything that can catch their hair, which would include a living hinge as well as exterior fingers as on the GF design. I think people with really short hair might say the same thing. For this reason, I made the adjustability portion of my Gecko design on the interior and so far I’ve gotten good feedback (though I’m continuing to gather feedback).
As Geek2Nurse noted, the hinge is harder to clean and I’ll add that it is also more breakable.
On placement, I’ve seen two positions work and one not. Working: Bottom of head with both straps below ears; middle of head with straps above/below ears. Not working: top of head with both straps above ears.
Some people have suggested that the best cradling/confirming design is with flexible plastic, not a living hinge. I think this is a good point, but I didn’t have any such plastic, so my first designs were for the acrylic people seemed to be using and is in good supply. I have some Lucent (from Johnson Plastics) arriving on Wednesday and I have a design I’ve made specifically for it that I am anxious to test. I don’t have any PETG and I don’t know how its properties compare with Lucent, but that is another flexible plastic.