Having BOTH lengths ... yes the 35" will make greater power at any given pressure and will be quieter .....
There is some trade offs in play Recoil launching heavy .30's is not going away no matter length of barrel, So .... a shorter barrel ( The OEM 25" ) has IMO the edge on accuracy or lets say easier to shoot accurately. As the resulting muzzle flip will have the projectile clear muzzle sooner in a shorter barrel as muzzle moves upward over the longer barrel.
Harmonics might be another with the longer barrel an additional 10" further out from the front holder/collar it may effect it somewhat ?
Now said ... BOTH barrel lengths shot fantastic and was using the 35" near exclusively because it was a lot quieter and more air efficient.
I've gone over to .22 cal in my personal EPOCH at for now a 25" length in OEM shroud. If & when SKOUT releases a .22 cal "LONG" 35" SLUG liner the long set up with likely go back on.