Yes , Some directories only allow the premium e.g featured listings to be listed on the top level categories and as we know that top level categories has all the juice so obviously premium make difference as compared to free,If your paying it means the seller is has something that is not in the free you know world
yes, premium listings do help in a way. your site gets displayed in the top if you have a premium listing option. and therefore you get advantage over the other free listings. However, i prefer the free listings
Premium listings provides a much more efficient way of promoting and reaching your target audience than normal/regular listings.