Pick whatever you want and use a BRT gas tube.

I just received a RifleSpeed built upper with a Criterion Core CL barrel in 11.5”. I only put 30 rounds or so through it so far but am shocked at how well it works. My suppressor is a YHM Turbo K with direct thread mount and the lower has an H2 buffer and a Tubb buffer spring. I’m left handed and am used to being blasted in the face from back pressure, but this setup had nothing coming back in my face. I’m also using a Radian Raptor SD charging handle, but it didn’t do much if anything in prior uppers without an adjustable gas block. The gun shoots flat and soft like a longer gun with compensator.

Crane did some studies that are public. Parts life, group size, throat erosion and higher bolt velocity were tracked and/or demonstrated.

They must be watching this thread, price is up to $350 matching the other vendor you posted.

@TGWLDR

Well shit.