What do you all think is the very highest quality Tint?

I have just installed Expel Nano Ceramic Prime XR Plus: - 5% roofs, 15% sides & rear, and 35% front. It is very good, but I still wonder about the German made Huper Optk
https://www.xpel.com/products/window...ve-window-tint
https://www.huperoptikusa.com/automotive/

I know there are others 3M and and. But I am hoping this thread will rouse the engineering experts on the forum. Can we dig in to the deeper specs not just the marketing BS which as we all know in recent years has decimated our society with advertising over engineering substance. The top shops I know rave about Expel but my installer said it felt just a little thin (he is not a top expert). I have no idea of the significance of that. I do know ceramic allows cell phone waves through much better than regular tint. I also know Xpel looks fantastic. But has anyone used Huper and is there anything higher end than that???

(talking of high end does anyone have an older Nakamichi head unit in their X351??? - I have one in another car of mine and OMG - what a difference - literally staggering, but no real advertising or marketing on that head unit. They spent the money on the engineering... (maybe Boeing should try that; they just appointed another bean counter as CEO WTF)