You both suck.
Its a matter of saving money. Obviously you inspect the block and mains for damage and as I said...assuming it didn't cause damage to the mains then you'd be ok. (that's what "...didn't melt down next to a main.." sort of means)
Either way, if you take the normal precautions like put the mains together and re-measure the bore of each main from two axes, then you'll know if damage took place.
I personally would go the cheaper of the two routes, crank then block UNLESS the cost was about the same. However, from my own personal experience a newer used engine is the cheapest way to go in almost all cases.
Tom
