On a pug team with 5 dps, is it better to be the one tank with no healer or the one healer with no tank?

Similar question if there's only one of each and 3 dps.

Basically, if you're in a badly-picked team and don't feel like quitting or asking other people to re-pick, does the priority go to tanking or healing? Assuming you're equally good/bad with both.