Both my current horses have/had HJ bridles. At first both had 3 D heads.
I wasn’t convinced they made any difference. I sold them, simply because one horse retired and one needed a new saddle which was the wrong colour. I did replace Ziggys with another HJ as they are so lovely but he just has a normal head piece and I prefer it. It’s neater looking and he is the same in it, obviously from the above I’m the minority!
I’ve also done a DIY around the 3D headpiece. My boy seems very
happy in it generally, but he’s got a LOT of forelock which gets stuck under the cushions and if I forget to pull it all to the middle before taking the bridle off we have to do a little dance about to get it unstuck. That is very annoying.