This is kind of really just a straight upgrade right? How often do you really need to tap down 1-mana creatures? Granted, it can't tap down a big token but you hopefully have more removal in the deck.
There's a handful of fringe scenarios when tapping down a 1cmc creature with a tap ability is useful for forcing an action:
etc...but if you are running Gideon's Lawkeeper, you're probably not running many of those culprits.
Other good targets to tap down with lawkeeper:
But most likely, it's ability to block 1/1s or not die to other sources of 1 damage far outweighs it's slight disadvantages.