Izzy overall All Time as well honestly.
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Henderson has a spotty record. He'll win some and lose some.
Won a split decision against Big Nog (so argubily didn't win) but then lost to Big Nog by armbar in their next two fights
Lost to Wanderlei in 2000 Decision (unanimous). He KOS Wanderlei in 07 but keep in mind Wanderlei was coming off the brutal Cro Cop head kick loss.
Lost to Rampage
Lost to Anderson
Kos Bisping
Losses to Jake Shields
Gets a lucky low % ko win over Fedor
Has two amazing wins against Shogun
Loses a split decision to Lyoto
Loses a split decision to Rashad Evans
He also lost to Vitor a couple of times by finish (but I don't these against him because this was Vitor while on steroids)
Tko'd by Mousasi
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Izzy's Pereira win is better then any of Dan's wins other then Fedor. (Because Fedor is an elite grappler as well)
Pereira is a way more elite striker then prime Wanderlei or Shogun, weight drained or not.
I can admit this as Shogun/Wanderlei fan boy from back in the old days.
I can't really say a singular win over Fedor is enough to put Dan over Adesanya who has multiple title defenses.
I do agree Dan mostly had tougher fights but a majority of those "tougher" fights he lost.
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As far as who I think would win in a fight between prime Hendo and prime Izzy, I could see it going either way.
That's a tough fight.