I like both games and think they are two of the best games Trudeau designed. For me the theme of Creech and how both the Creature and the drive in movie are tied together are a theme I really like much more than Congo. I owned a Creech and really miss it. However, if I'm sometime in the future in the market for a pin and happen to find a Congo for a reasonable price I'd get it.
For me it's Creech mainly based on theme.