Vector graphics biggest advantage is in how computers store them and render them... they're easier to scale and their native format takes up less space on the harddrive (in most cases)...

Also, pretty much any software you'd use to put the novel together and send to a publisher or printer's gonna convert the vector graphic to a raster format in the end. I'd say go with raster... now if you're looking for someone to do the map... then they'll go with what they're comfortable with... and in the end probably send you a raster image.