FF will always be FF, CF will always be CF, CF will always lose out due to crop factor (50mm to the crop factor of 50mm x 1.6 for Canon and 50mm x 1.5 for Nikon) while FF is what you see is what u get focal length (50mm will be 50mm) using the same lens (dun talk about lens meants for crop factor) to compare. This is unbeatable, now and forever, unless once day CF is totally phase out and replaced solely by FF. This is one thing CF can never beats or even on par with FF.
using good lens (L lens for example) on FF and CF had its on differences too. On FF, it resolves and maximises the full capability of the L lens while on CF, it only crops the center part of the L lens. But dun be mistaken, sometimes good lenses (L lenses for example) also cause problem on FF, for example, you get quite bad distortion using a 17-40L on a FF as compared to using it on a CF but image quality wise, FF is still better and gives more details. FF outputs more details then CF in photos although you can still use PP to maximises out the details produced by CF photos but FF wise, you can save this extra step.
but saying this FF had it's disadvantages too. When comes to macro and nature (wildlife and/or birding) shoots, CF definitely holds more advantage over FF due to the crop factor. Using a FF on a 200mm lens, u probably had to walk nearer to the lion and risk eated up by the lion but using a CF on a 200mm lens, you can stand further back without the danger of being eaten up.
and lastly, it really depends on what you like to shoot and your budget.
Landscape, Portraits - No budget? Go FF, you will not regret it. Else CF is still fine.
Macro or Nature (wildlife and/or birding) - No budget? Stay on CF but invest in longer lenses, no point getting FF for this. Else just stay on CF.