Fit at any weight would of course be better, but over fat is so strongly linked with so many health problems (diabetes, sleep apnea, blood clots, leg cellulitis, hypertension, heart disease, gall stones, & more) that I doubt fit can trump it. For example, exercise can help control blood sugars in type 2 diabetes, but losing fat can make it go away entirely in many people. Same with sleep apnea & hypertension.
In our intensive care unit, obese people far far outnumber thin/normal. No matter what put them there (even trauma), they don't seem to recover as well, either.
My gut feeling is the "fit & fat" movement is more about feeling better about oneself. That's not a bad thing, except if it allows people to stay in denial about what they can do for themselves.