Variety. White Labs and Wyeast produce a lot of variety in their lines of liquid yeasts. Companies like Fermentis and Danstar (Lallemand) only produce a few limited selections of dried yeasts. Other than that, both dry and liquid yeasts can produce good quality beers provided you pitch the proper amount and re-hydrate the dried yeast.
Beer so good, it's frightening.
2014: Seven Heavens Series One: Vilon, Mystic Melomel, Skeeter Pee.