Hi Simon,

There are a few differences and things you want to keep in mind:

-By adjusting loft on a wedge you manipulate bounce at the same rate, so in this case you are either adding or subtracting one degree.
-When adding or decreasing loft you are also changing the amount of offset on the club (less loft = more offset, more loft = less offset). There is not a exact science to the amount it changes, but it is noticeable to some players.
-The TX4 groove design transitions from narrow deeper grooves on the 54 to wider shallower grooves on the 56. If this club will primarily be used for full shots bending the 54 could be a better option because the grooves are more suited for faster full swing shots. If this club will mostly be used around the green the 56 could prove advantageous because the wider grooves do a better job of displacing debris between the club face and ball at slower swing speeds.

We always recommend seeking the advice of your local authorized fitter, and testing the two clubs side-by-side to determine which is best for your game.

Let us know how it goes!