Well there is definetly a difference among Vice admirals.Just think about it this way;it seems that there is only a place for three admirals in the marine which means that from all the vice admirals on the armee,only three will make the grade.Now it doesn't means that the choosen ones are the only ones from the plot which are on an admiral level,it just means that the government chose the top three to become admirals.
From that,it is easy to assumed that there are still many Vice admirals that are on/close to the admiral level regardless of there title.So just like the Shichibukais,there should a huge difference among some of the Vice admirals in term of strenght.
About the Law-Vergo-Smoker issue,i would say that Vergo definitely is stronger than smoker and the best way to come up with that conclusion is to got back to the fight which opposed
Law to Smoker.See Smoker didn't lose to Law because he was weaker than him.In the contrary when you take a look at that fight,just by observing the power of Smoker's attacks it is easy to see that he was definitely the strongest.So for me reason why Smoker lost to Traffy is because Smoker's technic and speed were the weakest.Law was the fastest and that is why he won the battle and it is also the reason why he(Law) lost to Vergo.Now,i know many of Traffy fans will get the excuse that Vergo has his hearth

but if you take a look at
this panel it should be clear to see that haven though he retrieved his hearth Law barely had the time react that he lost it again so much he couldn't see what was coming.
Law lost Vergo because Vergo have both speed and the strenght of a beast and it is the same reason why Smoker will lose to him.He simply isn't fast enough.
---------- Post added at 11:28 PM ---------- Previous post was at 11:02 PM ----------
Also Luffy did take alot of the spot light since the time skip and it should be the time for other members of the crew to show what they can do.Like Mani with the fact that she controls the weather should be a good opponent against Monet.I am dying to see Ussop in a big fight so we can really see his improvement

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Note: the Allegory of the cave is definitely on top three of my favorite(number being "Men become they think"from Earl Nightingale) thanks for the reminding
