It's a lot easier to obtain a good hitter than a good pitcher. That's simply a case of depth. There are so few top calibre starting pitchers that they RARELY become available.

You can stock up with an awesome offense, but you'll rarely win without decent starting pitching. Whereas I think an awesome pitching staff will win with mediocre hitting. You can take advantage of the platoon and use lower ranked hitters to provide good offense. Even part time hitters can be very effective in a platoon role. Lower ranked hitters can be obtained in the middle of the FA draft and can fill a position with decent offense. Lower ranked pitchers guarantee nothing.

Hitters can have off years and injuries. Perhaps pitchers are slightly more risky but that depends on the individual. To me it doesn't justify lowering a pitcher's value just because he "might" get injured. Good starting pitchers tend to maintain their value in their late 30's better than hitters. In fact they can even get better. Obtaining a proven, good starter is a good long term investment.

I think a pitcher with a PB value of 6.000 is worth a lot more than hitter with a PB value of 6.000