I've been using the 58-08M bent to 57 for most of the year. Decided to add a 60-14K as an extra lob wedge and use a 56-08M for a sand wedge. Wedge setup is 44-50-56-60-64. I played 50-57-64 basically for about 2 years now. 54-08M is pretty deadly for chipping and pitching but leaves a lot to be desired out of greenside bunkers.
Mathematically, the difference in distance should be about 4-5 yards based on Maltby charts (2.5 yards for shaft length difference of 1/4" and about 1.25 for 1* loft). I was seeing a difference of about 7-10 yards on full swings (both square and open pitch). About 3 yards out of sand and about 5 feet on a 1/4 swing pitch. It seemed like the 56 felt crisper on chipping.
I hit both reasonably well and would go to the 58-08M for a "Sunday bag".
I experience another thing unusual: bent a 46-10 to 44. Mathematically it should have 3-5 yards but it was 10.