My take from internet lore and looking at both with a magnifier is they start out as the same formula from the original Swiss military loads and then get slightly different retardant coatings.

The color is different between the two. I also I have heard that R22 is a bulk powder with a +/- 10% variation and MRP is a canister grade powder with a +/- 5% variation. I may not have those numbers right but it does explain the greater lot to lot variation of R22 opposed to MRP. They load practically identically but if there is a difference MRP seems a hair slower burning but this is probably due to the lot to lot variation more than actual burning rates.

"When you disarm the people, you commence to offend them and show that you distrust them either through cowardice or lack of confidence, and both of these opinions generate hatred." Niccolo Machiavelli