Absolute fact that a longer barrel, with equivalent choke, will pattern tighter than a shorter barrel, with all else being equal.
This is due to the pressure drop in the barrel as length increases causing less shot column disruption (once it clears the bore) by the "jet effect" of the gas after the wad clears the crown. That releases the gas to freely accelerate and "impact" the rear of the wad/shot stack. This effect will be more pronounced when none or little choke is present, since the shot has minimal or no choke effect that de-couples the pellet stack somewhat, and moreso in a tight choke.
The choke has a recoil effect by having the fuller choke act as a more efficient rocket nozzle to increase the efficiency of the jet effect by the gas venting out the muzzle.
That is why porting will have some small effect on recoil and sometimes cause increased pattern density - by reducing the gas jet rocketing out the muzzle.