The City, Twiggy and Part Time all have the extra shoulder strap. I had a 2006 Black City which I loved but finally ended up selling it because I couldn't love it as a shoulder bag using the strap. I found it would swing around and get in the way. To me these bags are gorgeous when carried over the arm or by the handles. I'm a 100% shoulder bag girl so the City just didn't work for me. I think the Day and the Hobo are intended to be used as shoulder bags and look better on the shoulder than when carried over the arm. JMHO. Between those two, the Day is longer, narrower and deeper than the Hobo and probably holds more so it just depends on what you are looking for.