OBP covers 1,000 points while SLG covers 4,000. I'm sure that's part of it, but with the fascination with OPS, it's good to realize all OPS are not created equal. I fell victim to that when I didn't give Clark his props for having a high OBP. Hardball times uses a stat called GPA: "Gross Production Average, a variation of OPS, but more accurate and easier to interpret. The exact formula is (OBP*1.8+SLG)/4, adjusted for ballpark factor. The scale of GPA is similar to BA: .200 is lousy, .265 is around average and .300 is a star." They say 1.8, so far this year it's been 1.6, but the idea remains the same; comparing just OPS's of two players isn't really fair since OBP is that much more important.