I'd favour Ngannou, I do think there was some hold over from the Stipe loss mentally at play here.
That said I think an opponent with a good chin and power to fire back is arguebly more of a test than the guys Ngannou has been beating, cracked chins like JDS and Reem or guys like Bladyes who arent natural strikers.
if Ngannou pushed harder for a stoppage but didnt get it I could see Lewis having the edge as well, I think he's someone who can "tight tired" and remain dangerous, maybe not to the degree of Mark Hunt but still perhaps more than Francis.