The shorter, the better!
Long links are boring. Short links can be typed on a keyboard whithout falling asleep...
And on most keyboards, the dot key is slightly easier to find than the slashe key. That's why 3W.IO produces short urls without slashes! isn't that wonderfull? (Okay, we mean besides the "http://" string of course. That we cannot change.)
Sherry on the cake, links can be edited later. Yeap. And it's free.