What's interesting about Pyrodex is that the pellets are actually a little more powerful than the loose powder, while 777 is the opposite (the pellets are a little weaker than the loose powder).
This shows that Pyodex likes to be more denselycompacted, and as long as it's done consistently the velocity won't deviate as much.
Pyrodex P is said to burn even cleaner than the RS.
But power isn't everything since sometimes the most accurate loads are not necessarilythe highest velocity loads.