The Sims 3 definitely has some amazing looking worlds. At this point, I'd have to give that edge to the Sims 3. The Sims 4 has nice worlds too, especially Windenburg, but the Sims 3 also has the added bonus of more variety in its worlds at the moment, on top of them being so great.
As far as the Sims themselves are concerned, the Sims 4 hands down is better to me. I'm not saying it's impossible to make good looking Sims in it because I've seen many great looking Sims made by people, but many Sims I've made, and NPCs, have had that kind of same looking face going on. Like some have called it, "pudding face". Not a big fan of that.
