For those who play in pub quiz teams (here's one for you Meike) Canada has the longest coastline using either measurement.
How about this for an interesting (and totally useless) piece of information: The country with the coastline to highest land mass ratio in the world is the Coral Sea Islands with a landmass >3 km², a coastline of 3,095 km and a land/coast ratio of >1,000,000. Next, wait for it, comes the Spratly Islands with a landmass >5 km², a coastline of 926 km and a land/coast ratio of ≥200,000.
The where? I have to confess never even having heard of the Spratly Islands. It turns out that they are not a country as such and have no native inhabitants. However about 45 of the islands are occupied by relatively small numbers of military forces from China, the Taiwan, Vietnam, the Philippines, and Malaysia.
Well didn't you just want to know all that?