Aesthically, in real life, I think they are slightly nicer than ultras.
Comfort definitely goes to the ultras but the Y3s are still a very comfortable shoe. Slightly more structure which I prefer.
Sizing: to echo others, I would recommend .5 down from TTS. Therefore, if like me you go up .5 for your ultras I would go down one full size from my ultra sizing. If you went TTS for ultras only go down .5.