Weight: system more important than sensor size?

When the exact same exposure on the different formats represents the "best" shot for each.  For example, if the best shot was 50mm f/2 1/200 ISO 400 on mFT, 100mm f/2 1/200 ISO 400 on FF would be the best shot for FF is the lesser DOF and/or lesser noise was more desirable than the deeper DOF of the mFT shot.

However, if not, then the best shot for FF would be 100mm f/4 1/200 ISO 1600, which would be the equivalent to the mFT photo, although some intermediate balance, like 100mm f/2.8 1/200 ISO 800 might be better still.

As you and I say, the competent photographer must balance exposure with DOF, motion blur, and blown highlights.  In the situations where the same exposure represents the best balance of the other elements, then the same exposure on different systems represents the best shot, even if the pics look different.