Coke did blind tests at the time that showed New Coke was more popular (it's been too long, but I feel like there were some independent tests during the scandal time as well). The outrage when they released New Coke was all about nostalgia, nothing to do with taste. People were simply offended that Coke would have the audacity to change the flavor they were accustomed to.

I still remember the scandal. It was hilarious. There was a recent redux on a smaller scale when they modified the recipe for Coke Zero.

IIRC, the big difference between diet coke and coke zero is that one is based loosely on the formula for coca cola classic, and the other new coke. That may be an urban legend, though.