Agreed with skunk. None of them are used by the game.
RC27 could be useful as an aggregator (similar to ERC# for pitchers) but, in practice, it is not a very good one. For example, anyone who has played high cap leagues can tell you that 1920 Babe Ruth is more valuable than 2004 Barry Bonds, but 2004 Barry Bonds scores 3 runs better in terms of RC27. This may be due to the fact that RC27 doesn't take into account normalization, which is a big factor in this game.