Difficult question. I had to weigh the question between Showtime, Pets and Island Paradise. I haven't used any of the worlds that came with these expansions yet (only tried out Starlight Shores for a few hours). Showtime and Island Paradise come with some of my favorite clothes though. I find Showtime the most disruptive for the game (all Bridgeport bar mixologists etc. are forced into those Showtime careers and wear those clothes on their jobs). I never play those careers, but I've made use of a genie once in a while. While I like pets in real life, I'm not fond of them in the game. Pets' saving grace is its synergy with Supernatural, and boy has it a lot of objects that aren't pet-related with several complete furniture sets, for example. Regarding Island Paradise, I simply don't use anything from it, aside from the occasional windsurfing during university stays and the clothes.
The poll winner ITF is not on my shortlist for cancellation. It comes with lots of furniture sets, the soil rugs and transparent roof rugs that I pretty much always use in worlds with autumn and winter, or cafeteria lots. While my families don't travel to the world very often, I have great memories of family stays there. I also use a plumbot for automatic gardening if the family doesn't need the skill, and I usually produce those in Oasis Landing. The elevator tubes also have their uses once in a while.
