It's generally about a club for every inch you choak up. But also depends on the type of shot you are playing. If you try to play a high fade, you might be able to get away with the same distances in dry conditions. Normal to draws need a the extra since there will be absoutly no run after the splat.

Trying to play the ball forward to gain the extra hight and carry can be dangerous if not struck just right. The devistation of anything even remotly fat will not only cause the ball to go nowhere, but you better have a towel available to clean you off.

My perference is always to try to pick is as clean as you can..erroring on the side of thin.