Melatonin is better for sleep compared to valerian as melatonin aids the production of sleep related problems in people suffering from sleep related issues, whereas valerian root seeks to alleviate stress and anxiety related problems to coax sleep onset. Another way to look at the difference between melatonin and valerian root is that while melatonin is a hormonal sleep aid, valerian root is herbal and as such Melatonin is more direct than valerian, so it can be more intense in its effect.  However, the similarity is that both melatonin and valerian root tend to make people feel groggy the next day.