I really love AK, and we spent two days there on our last trip. However, we spent two days at Epcot as well and I didn't get to do everything I wanted to do. I guess it depends on how you do World Showcase. I like to explore the stores in each world, get the passport stamped, watch the various shows (some are really good and cool - loved the drumming in Japan for example, and the waiters in France etc.). Plus there are so many things to do and see in FW.
So, I would go for a second day to Epcot to finish world showcase.
So, I would go for a second day to Epcot to finish world showcase.