I think the main difference is that the zero sugar ones do taste more like the regular sodas do, and they also seem to be using different sweeteners to get there, but not sure if that's better for us or worse. Splenda and stevia are better but usually they aren't using those.
For instance diet coke in my opinion tastes horrible and didn't even try to taste like coke does. But the zero sugar coke is a lot better and does do a good job as a stand-in for real coke flavor.
