Case study, Bleach: tools vs transformation

There's a theory I've had for a while and been collecting examples of: that, in anime and manga that feature both possibilities, power externalized as a tool is generally beneficial, or at least controllable, while power internalized as a transformation will generally get out of hand. Bleach has been my flagship example for a long time now.

I'm waiting to see whether the latest turn will bear out or run against this theory.

( Necessary spoilers )

Which means that, even as Naruto and KHR devolve into the uninteresting and the forced, I have at least one series I'm hanging on, week by week.