What retooling more critically affected each series? Red Sky or Fast Forward?

[pannoni1]

Red Sky and Fast Forward both marked sudden paradigm shifts for each series; the main differences being Red Sky marked a transition from light to dark (though Season 7 shows some hints of this), and Fast Forward goes from dark to light. Both often considered "jump the shark" moments for each series, they came at a time when the creators were desparate for each series to get back on its feet, but ultimately fails to a degree. Still, I believe Fast Forward was much more critical in affecting the 4Kids series; not only is there a dark to light paradigm shift, but there is also a semi-permanent time switch, which eliminates most of the primary supporting characters outside of the turtles and I feel that the shift was "too abrupt". At least with Red Sky, you still have the same villians (even if some new characters or new mutations are introduced), and continues to take place in a present-day universe.