The most accurate 1/6 helmet ever made is the Gentle Giant Stormtrooper mini-bust, though it has the mic tips a bit too long and the helmet itself is a tad too small. But in the end the sculpt itself is the best there is, and for a simple reason, they scanned a screen used helmet and scaled it down. That didn't happen with their Stormtrooper statue, neither the new mini-bust. In 1/3 the most accurate is the SFS scaled helmet, once available at RS Prop Masters also present on the Judge Dredd 1/3 Stormtrooper statue.
I'm also a big Stormtrooper fan, my general collecting focus being Original Trilogy Imperials and Troopers, and particular focus being Stormtroopers - you can check out my collection thread in my signature. I'm a so called "rivet counter" regarding accuracy. If you look at my older posts in this thread, and HT Sandtrooper thread, as well as Sideshow Stormtrooper and Sandtrooper threads, you'll see my opinion regarding the lack of decent accuracy on SSC figures and statues. HT Stormie is much improved over the SSC, but not perfect. Still I like the HT figure a lot, I own 2 tall versions, a short one, a Spacetrooper, 2 orange pauldron Sandies, and waiting for white (and black) pauldron Sandie, ROTJ Stormtrooper and Han Stormie.