Rg and Diff numbers are simply a measuring stick for that balls energy. It is a bad policy to attempt to compare numbers from one ball to the next in regard to performance since it does not take into account geometry.
Use the numbers to determine if a ball is a low rg or high rg low diff or high diff is fine but do not make the mistake of attempting to compare ball to ball simply by the numbers, it the entire system that makes the difference. Core shape, cover make up and surface friction.