I agree with Kanga that if the choice is between one day in Santiago or one in Finisterre, I would definitely pick Santiago.
I also think that a lot (most?) of the raves about Finistere come from people who walk there. It is just an awesome experience to walk west till you can walk no further. And if you're lucky enough to see the sunset, wow wow. But as fishing villages go, it is pretty, yes, but there are many other very pretty seaside villages along the coast in Spain. I know beauty is very subjective, but I think many would agree that some of the seaside towns and villages along the Norte are much "prettier."
My first Camino ended in Santiago and we took a bus to Finisterre and spent a night there. Enjoyable, some good food, but it absolutely didn't pack the same punch as when I have walked there. But maybe that's just me. I'm not trying to discourage people from going there in a bus or a car, but just think that the experience is very different when you walk. Buen camino, Laurie