Another difference is that the critical tables have staggered and knockback as effects. It should be no difficulty to translate these into RMFRP terms, but it is something that the players will notice if they pay attention. They might also notice they get new critical descriptions instead of the old familiar ones.
From another perspective, we are not speaking about the Armory kind of woes where you had to look at the Armslaw text to determine what the result really meant. There were readability problems with the first RMU version. Now after Ironcrown cleared up the symbols, I think the critical tables have become the most user-friendly ever. I have difficulty seeing why not everyone would prefer to switch to the new critical tables.