Interested in picking up the 19 and 30mm. I will probably buy them both through B&H's 2-for-200 offer, but I was just curious whether the old style lenses are somehow inferior to the new "Art" models? At twice the price I'm wondering whether they're just trying to create a premium market for the new lenses, or whether there is actually something new and improved about these lenses, optically? Curious about any other changes as well, aside from the smooth finish. Sorry if this is a duplicate, I didn't see any other threads about this specific query. Thanks!