So much depends on the coin. If it is damaged, worn, holes drilled in it, etc there is not much of a demand for it as a coin to be collected. If it is a rare date and in great condition, it could be worth hundreds, thousands and in some rare instances, millions. If you had a 1913 Liberty Head Nickel and had it melted down for the silver, you should be committed to some place where men in white coats could discuss the situation with you. I myself just can't imagine why anyone would ask that question during a coin collecting boom like we are having at the present time.
Possibly another way to look at that question is which is better to do with a 1957 Chevy. Sell as a collectable or have it melted down for the steel?
AHHH, but just think of all the copper you could get out of the 5 known. Could be melted down for nice house wiring. The Nickel could be used for gun shell casings.