It really depends what specs you're going for.
If you're a feral sort like me, then DPS doesn't matter, as animals have a static hit speed and power based on stats, not the weapon's damage rating.
Also, hit procs (IE: Bleed on hit, shadow bolt, etc) don't work in animals forms.
So I picked whichever weapon I found that had the most agility and was cheapest at the auction house.
For restoration druids though, you may want to go with a staff until you find something really awesome to go in your off-hand.
If you're feral, the melee damage doesn't really effect you, and if you're restore or balance spec'd, you probably don't melee much anyhow.
If you're a balance druid, go for something with spell damage increase, if you're restore, something with high intellect and +healing.
Basically, whatever works with what you're planning to do.
There's nothing wrong with staves for my druid, but if a better weapon comes along, I'll switch weapon types to match. It doesn't take all that long to train weapon skills.