Sephiroth's mobility might be slower in Bizarro or Safer form (I doubt it would be though in Safer) but still his defense is much more stronger. I mean just compare hit points between Sephiroth and Safer Sephiroth.
Sephiroth: about 5,200
Safer Sephiroth: about 72,000
and if all of your characters are maxed out, then Safer Sephiroth's hit points get extremely higher as a result. So any way you put it the two forms would help Sephiroth out that is if we are using them.
Threaded Mode