I think you should experience Sims3 Island Paradise, because why not? :) What I loved was the houseboats, diving under water, introduction to mermaids,and the all-in-one bathrooms. What I did not like was the land itself? Living there was a no no for me. Wasn't beautiful and too bad my sims couldn't visit from other worlds instead. It took forever for my sims to travel anywhere. Oh! and the life guard career was fun. lol I can't remember what kind of treasure was found in the chests.
Sims4 Island living, I love the premade sims, the world is beautiful, I love that my sims can live there and or set up a generic lot for sims to stay the weekend if you want. Tanning, the floaties, and swimming I enjoy more in sims4, even though they can of course do this in sims3. It would have been very nice to have the life guard being an active career but it's fine otherwise. I enjoy the boats and jet skis in both iterations. I have not experienced the festival, drink kava, the volcano balls, conservationist, meet a mermaid except in human form. I am very interested in the ancestral ghost stuff since I enjoy supernatral elements in sims. I've yet to experience it much. I've only seen the little spirits at one of the premades' house. It was creepy but cool.
@tulipssimmer I think you can enjoy something from both sims3 and 4. Have fun. <3
