Pros: 1) Strangerville offers you a story. 2) Strangerville events are self contained and won't affect other world. 3) Some hidden stuff is actually pretty cool. 4) Reasonably useful stuff is added to the game if you are a builder, both normal and debug.
Cons: 1) Once you have done it once you probably won't do it again as there is very limited variation in decision making. 2) Aspiration is essentially a tutorial abd a guide for the story even though it's reward is kinda okay. 3) Personal opinion is that the new world is kind of dreary.
I think Sims 4 has potential for more story based content and Streangerville offers exactly that. What it does it does not too shabbily but it doesn't do much beyond that.