To me, vetiver has a sweet, cool, moist, earth-like scent. Very heavy and damp.
Sandalwood on the other hand is dry, smooth, light and generally warmer. Depending on the blend its in sandalwood can take on sweeter, sharper, or almost cedary aspects. Good sandalwood (the best was and is still from Mysore, India) is much harder to come by now. Since many of the Mysore trees have been used up it's distilled from other places now or produced synthetically.