My guess would be it depends on the class. IE alchemists would need more magical crafting than normal crafting.

But then I checked out a list of the most powerful tools in the game... seems like off-hand items are more likely to have more MC, but they are higher level too. So it could be primary hand items need more crafting while some offhand items need more MC. Now some professions like GLD have items which in general have more crafting, and some like armorer seem more balanced.