One way to think about the question is to ask what diameter would the bullet have to be for the rifle shot to have the same margin of error as the pool shot.
I won't bore you with the details, but I did a quick calculation that assumed a 9' table with 4.5" pockets. For the same margin of error, you'd have to use a bullet with a diameter of about 0.75"! That's slightly larger than the dime (0.705"D) and much larger than any caliber you'd see on a shooting range
Therefore, the rifle shot requires much more accuracy for typical calibers (caliber is roughly equivalent to bullet diameter.)
As others have stated, however, the comparison is pretty meaningless as the skills required are so different.
Robert