Interesting to note:-
Fujitora has never been sneak attacked in the series. Whilst of course other Admirals and GB have. This is to show how good Fuji's CoO is.
However GB noting how well Yamato's haki is...shows he knows what hes talking about and that hes a CoA specialist....possibly even has CoC.
With Fuji being bruised by DR Luffy (for 1 panel) and GB being unscathed to an AdvCoC attack from Yamato....pretty safe to say GB is more durable.
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So far in defence, GB is superior. He has blackblade, better durability, better CoA, Logia Intangibility. However Fuji makes up with it with his CoO.
Likewise Fuji has better offence, with his destructive and OP Gravity Fruit, but GB is not far away with his Plant Fruit and its hax.
Both are pretty balanced and its an extreme diff either way if they fight.