I, personally, think that misting is way more important. Misting isn't just important for drinking and humidity, but it plays a part in keeping their eyes clean and their skin healthy. I do a couple mists a day that are 15-20 minutes long and my chameleons will sit under the nozzle (instead of being in the dry corner) the entire time, rolling their eyes to wash them out and just to soak their skin.
If you can do both, great. If you can only do one, I say do misting. And do mistings longer than 3-4 minutes if you can.