answer:They’re both made with aspartame, which turns into formaldehyde when it hits 86 degrees, if I remember correctly. Yes, they have zero calories. Legally, I believe they’re allowed to have less than .5 calories per serving and still say “zero calories”. But really, you’re going to burn .5 calories swallowing the stuff anyhow. That said, I’d rather drink formaldehyde than High Fructose corn syrup, mostly because HFCS is so friggin’ addicting. I can drink a Cherry Coke Zero today and not need one tomorrow. I have a great compromise – my grocery store brand diet soda is made with Splenda. No aspartame! And it tastes better, too. And and, it’s cheaper.