Ground rpm reading comparisons are fun to do but really aren't very informative. They'll tell you if each prop is turning in an rpm range that OUGHT to work or not, but the difference between different props is vastly overrated. About all you can count on when one is faster than the other is that it's probably got less pitch or efficiency. And about half the time the slower one flies the plane better.

One of the best prop tests is to do two consecutive loops and simply judge how well the prop pulls the plane over the top on the 2nd one. It's completely subjective, but works pretty good in spite of that.