Chisora, although i would imagine that his career is going to suffer over the next few years. His motivation must be terrible. Imagine going from a massive fight against Wlad, to losing to Fury, to fight Big John.
Chisora if his motivation is sufficient to prepare properly (for the reasons outlined by modestbiggles). If Chisora is not really up for it (as seemed to be the case against Fury, bizarrely) then McDermott will probably overwhelm him. But I think Chisora would prepare properly and win, late or points.
Big John would school del boy , what's he really done , and who has he really beat ? As soon as he fought a live opponent he got beat . Big John gave fury a much harder fight than chisora and will get late stoppage or pts win .
Chisora would win, mainly because he's tougher mentally. McNugget seems like a bit of a headcase in there and is liable to full apart whenever he starts to doubt himself. Funny thing is, Maccy D i actually quite skilled when the confidence is in full flow.