Everyone has given great answers so far but I wanted to point out that since stevia tastes kinda bad, most stevia extracts I can find are actually mostly erythritol (another low cal sweetener) with a small portion of stevia. I find their marketing to be quite close to a lie, but in any case, both products are as safe as any transformed food you're gonna find, so fine with moderation. It can be argued to be better than sugar except if you wanna count the sugar taking habit, which both encourage.