Sims 3 all the way for me. I prefer the realistic style.
Now in some aspects the quality of the graphics is better, I like the skin textures on the sims better than the EA skins in TS3 for example. But I've also seen points in sims 4 when the graphics are downright awful (I had pics from when I had the trial, but I've lost them in wiping my laptop since then), so it's not flawless in quality either.
But I don't hate TS4's art style either, sometimes I do see shots out of it that are honestly stunning... granted they tend to be edited but so do some of TS3's most stunning shots (though I think it's easier to get to "stunning" without editing in TS3), but even edited they had to have something to build on so it's not all bad.
