"4P shadow is like 240 haste rating.
4p healing is like 250 spell power.
Those may not be the specific numbers, but that's the ballpark IIRC. "
Considering, 250 sp is much better for spriests than 240 haste, and i would blow a gcd every 10 seconds for 250 sp. Im way too tired to do the math, but, by using the holy set instead of the shadow set, it is apparent that you would lose some hit/crit, but you would prly gain spell power as a result, not to mention the set bonus for holy, im talking about the 250 sp, is much much better than the set bonus for shadow, the 240.