I'm not a fan of totally open worlds. Maybe more open neighborhoods/districts. However, I actually enjoy not having to control another Sim while I'm playing another member of the household. It was annoying to me in TS3 to command one Sim to do something in one place while I did something for another Sim in another place on the map. Because the one I left would run back home and didn't always follow commands. In TS4 I enjoyed (very much) taking two or more Sims somewhere, changing my mind and leaving the other there for a time while I went to another lot or spot with another Sim.
Then I could even take the Sim back home and the other one I left somewhere will eventually come home on their own. I really, really loved that about TS4 since I play large household most of the time in these games so yay, peace and quiet for a few hours. lol