I think what is meant is that in the vein of OPS, OBP and SLG are weighed equally, but they do not have equal value. Its been said that a true value would need to multiply OBP by 1.8. So Theriot, being a 402/383 (784 OPS) guy compared to say, Peralta who is a 307/486 (793 OPS) is actually better than Peralta despite his OPS being worse. If you multiply OBP by 1.8, Theriot has a 1107 adjusted OPS, and Peralta has a 1039 adjusted OPS. Tango created wOBA that does a better job than OPS by using run values of events. Comparing the two, Theriot has a 355 wOBA, whereas Peralta has a 336 wOBA. Slugging is really important, don't get me wrong, and I've been railing against Theriot for having a terrible terrible terrible IsoP (worst in the league before yesterday, thanks Gregor Blanco!), but that doesn't mean he hasn't been an above average player. Now, that doesn't mean that he'll be able to continue to produce above average results.