Ones better offensively, the other defensively.

GNW Hinata can provide an offset blitz and some defensive insurance of that turn. However, without that stacking defense/res passive, it makes her a lot squishier than her regular form.

As for her normal form, it's meant to be a defensive wall, which she provides best.
Her damage will mostly come from her chases.

It's really based on what you need and your playstyle.