With a patch precut round you always have the risk that this one is off-centered, so the risk that the bullet loses its accuracy, inversely with a patch cut at the muzzle this decentering problem disappears inevitably since the patch is cut to the right size and with the ball right in the center....
Personnely I found far better the cutting at the muzzle than the patches precut, the final detail is in at a match or competition: the time to cut the patch is longer than put a round patch precut.
This is sometime a choice and more in case of shooting a flintlock than shooting a percussion cap rifle. For us a match is during thirty minutes for thirteen bullets and the first shot is to prepare the rifle (we call this shot "Flambage"), that makes fourteen bullets and if a flint needs a change during those thirteen minutes could be too short when cutting the patches...