I like a slip on shoe because it's a lot easier to get on and off.  If I want to kick them off while I have my feet elevated on my couch, it is then very easy to put them back on if I get up to move around the house.  It's also very convenient when going through airports.  I particularly like that the wide width accomodates my bunion.  Whenever I wear shoes that tie, even double knotted, they seem to work themselves loose and I have to retie them.  This isn't very convenient if it happens while you are at work.  This is my third pair, and I'm sure, not my last.