I wasn't comparing regular soda to diet soda, I was comparing having diet soda to not having diet soda. Diet soda affects gut flora and insulin levels. Calories are not the whole story.
That has only been demonstrated in mice, however, and only with semi-unrealistically large dosages of sucralose, if memory serves me right.
In humans, we have a lot of evidence that shows that the source of calories does not matter, for fat loss. Long term health is another issue, of course.
IMHO, putting focus anywhere but on calories is doing oneself a very big disservice, except for some athletes and bodybuilders for whom other factors are important as well.
