You can both be right, because trying to make more conscious health decisions is what actually made you healthier.

Aspartame itself is completely safe, but recent studies have found all artificial sweeteners have metabolic effects. It's not that the chemicals themselves are hazardous, as you say aspartame in particular has been very rigorously studied, but that it appears the body uses the sweet taste as a signal to change insulin production.

Is it better to have a diet pop than sugar pop? Definitely and I prefer Diet Coke these days, Classic feels like drinking syrup.

However it's even healthier just to drink water, or non-caloric, unsweetened drinks like coffee or tea. Soft drinks are supposed to be a treat and not a food group, I drink maybe one a week.

I'm not going to say you're wrong about aspartame being safe because I don't know for sufe, but I question whether you're right. The fact that Donald Rumsfeld was the CEO of the company that held the patent, couldn't get it approved then magically got it approved after his buddy Ronald Reagan appointed him to a position where he could do so makes me wonder if it ever should have been approved.