There's definitely some kind of difference between sparkling water and seltzer water. I enjoy seltzer so much I even like it completely flavorless and I'll just drink that shit straight out of the can. The cheapest grocery store shit is the best. Sparkling water has this almost mild sugaryness to it (despite generally having no sugar) that really puts me off. It seems to occupy this no man's land between seltzer/club soda and just regular soda.