Purely based on gains...

You have to keep those items on to be at those higher ranges. But other than the obvious, no. There is no difference.

Except in the case of a Shapeshifter. Where it goes by your form stats (while in form), and your natural stats (not your natural + magic) stats. Which is a good reason to have max stats as a Shapeshifter.

Out of form it is the same as everyone else.