I know that many MOC builders buy large sets, such as the Unimog, 9398 Crawler, or Mobile Crane Mk II, just for the parts. Others use BL to get parts - many BL parts for sale seem to be parted out large sets current and recent. For BL, you pay a premium for someone doing the parting-out, but you only need to buy the parts needed.
My question is whether one uses all of the parts or some significant fraction if you by a large set. For example, of the 2600 parts in the Mobile Crane, how many are useful for MOC creations - all, most, or half? Should I be buying large sets, or just BL the parts I think I need.
thanks for replies and comments!