I believe this would be a very competitive fight, I lean towards Monzon by UD as I think his ring generalship and jab would carry the day.
Battle of the jabs. A hard fight for both these dudes. Monzon has a way to nullify what the other guy is doing and GGG fights in a similar way. I think that if it is mostly a ranged battle, Monzon has the advantage. Golovkin will have to cut the ring and turn it into a mid range battle with Monzon on the ropes. I don't think it would be a slugfest, although GGG would be advised to turn it into one if he could. Probably 50-50, I can find arguments for both.
I like Monzon to control the distance for the majority of this fight. Important for me is that Monzon has a whopping 6" of reach advantage while being an inch taller. Top shelf jabbers can jab with rangier guys and GGG established a superb jab in any number of fights. Monzon is a different level to what he faced however, he's a bonafide ATG with an ATG jab which is backed by a huge reach advantage. He's going to win the outside exchanges more often than not. He's also got a full array of punches, heavy hands and excellent footwork against incoming opponents. GGG won't be able to throw caution to the wind and will pay a price trying to close the gap throughout the fight. I like Monzon via competitive but clear decision personally.
