Is it important to use an alcohol based mouthwash?
Not at all. If you experience dry mouth, an alcohol based mouthwash exacerbates the problem. It depends if you're using mouthwash for cavity prevention (it needs to have fluoride) or for gum disease prevention (an alcohol based or prescription wash).
If you're using mouthwash instead of flossing, then you're going down the wrong path. Flossing does more for you that simply rinsing.