I made my choice to switch to artificial sweeteners 40 years ago. Around 10 years ago I realised how badly they had affected my health and opted for either no sweeteners at all or a small amount of sugar (rarely though). I did drink them to excess(2 litres a day for about 6 years maybe?) so that I felt full all the time and didn't eat as much food so that I could lose weight. My gut flora changed. My metabolism changed. I became insulin resistant. That's how I became morbidly obese.Though refined sugar has been proven to be harmful in many ways aspartame has not been proven to be harmful as yet so as I said for me its aspartame that's my choice You are free to make your own choice. I also prefer to use some form of sweetening in some of my drinks and food though again it's not a necessity I often do not bother to use any sweetener at all..
I don't see any harm in having diet drinks occasionally, but I feel duty bound to tell others what happened to me. It will remain anecdotal until someone shells out lots of money to do a good scientific study. This isn't likely as the food manufacturers and drugs companies would lose too much. So I expect it will remain anecdotal for many years to come....with ever increasing numbers of sufferers, all thinking that they are doing what's best for their bodies - just like I did.