This game isn't my favorite in large part due to the world being segmented into lots. It makes it seem very small and difficult to manage large households with different needs. Example: no more can you send one sim around town to do errands, while you control the other sims at home. The dialogue seems very shallow. No more can you have unexpected dialogues/outcomes with NPC sims. Also their mood swings give me whiplash. It's like dealing with a bunch of teenagers that never grow up. Toddlers have more going on, but that is a double edge sword. You have to carefully manage their needs if you want a cooperative sim that does more than just stand there throwing tantrums.
On a good note the different expansions give you some fun new activities to try. The vampires have more depth with a fun new tree. The various expansions get you more involved with your sims careers which is enjoyable. It is a lot more convenient to makeover your sim in game. The build mode has a handy option of picking your house up and moving it on the lot.
I prefer the sims 3(bugs, lag, and all). The game seems to have more depth. The entire town is one load time instead of multiple. The dialogue is more interesting because if you let them lead you never know where the conversation will go.