In most cases, it depends on the state of the table: A long tablecloth instantly improves a less-than-perfect table and adds a note of elegance for a special event, like a dinner party. Exceptional tabletops require no dressing at all. But sometimes you might want the softness of a tablecloth without completely obscuring interesting legs. In that case, go for a short one!
I can go both ways; I love a great tablecloth for the color and texture it brings to a tablescape, but I can certainly appreciate a stunning table that deserves to be seen at all times. Take a look and see what you think: