- most important: stay consistent - 1 URL == 1 page
- redirect one (wrong one) to the other (right one) via an HTTP 301 redirect
- then again if you have a website where different people work with: don't do trailing slashes.
in a perfect world people would just copy&paste an URL when they want to link to your stuff. sadly we do not live in a perfect world. people (i.e. pr guys, marketing) tend to typewrite URLs (don't ask me why, they just do....) and then again tend to forget the trailing slash at the end.
the wrong URLs in external links error rate is lower if you don't have trailing slashes.
but for most sites, it does not matter. choose one, stick with it.
