What would cause more condensation in the crawl space under a house, clothes dryer vented under floor or a/c ductwork?

The air conditioner. Dry exhaust duct would be hot and would not cause condensation.

What would cause more condensation in the crawl space under a house, clothes dryer vented under floor or a/c ductwork?

The dryer since it is driving about 2.5 gallons of water/moisture out of the cloths per load and placing it directly into the crawl space. By the way Cloths dryers are not allowed to be vented into the crawl space by code.

Note furnace duct work will not cause condensation UNLESS the A/C is running and the metal duct is uninsulated. If you insulate the duct properly the condensation problem in A/C mode goes away or if you use insulated flex duct to start with there is no condensation.

For clarification, is dryer vented into crawl space or through crawl space to outside?

I think the're both right. Cooler air can't hold as much moisture as warm air, Like when a cold front hits warm moist air, the cold air drops what it can't hold(rain).