This notion of impact of the bench is rubbish. Your best players start, whether that is Moore or TPN up to you but don't base your decision on who has a greater impact off the bench.
You cannot beat the top sides in this day and age without having 22 quality players. Impact players coming off the bench often determine the outcome of a test.
Far too often the Wallabies have lost close test matches against the ABs and SA because our replacements have not been able to play at the same level as those they have replaced.
Who is the better hooker out of Stephen Moore and TPN? Hard to say but Moore is probably better suited to starting and TPN will most likely have a bigger impact on the game coming from the bench with 30 minutes to go.
A fired up Luke Burgess can really change the pace of a test in the last quarter.
Rugby is now a game of 22 players rather than 15 players plus 7 replacements if needed.