alright man, check it out. i will agree that Mizukage could beat the Hokage, but i do not agree that Mizukage > Hokage.
*First i'd like to point out that Yin release is simply a different way of saying Genjutsu-user, so the whole "something from nothing/imagination" stuff is Genjutsu, it doesn't actually create something from nothing or anything like that, that's Izanagi-type shit.
*One of your biggest points is that Mizukage can absorb Water-based ninjutsu. Im sorry dude but i scoured the manga, went on narutowiki, searched databooks and nowhere did i see evidence he could actually absorb water attacks. so that one is out. But, lets just say for fun that he could do it. It wouldn't matter. Hokage can control his own water, so if Mizukage absorbed it, what would he do with it? get bigger? and even if so, there'd be a limit cuz otherwise his body would explode and he'd lose the water anyway.
*He can, however, merge with water--as in surrounding water, water that is available to him--as Suigetsu did against Killer Bee, the Giant Fish jutsu or whatever. That would make no difference either because of Hokage's ability to control water. If he surrounded himself with a huge mass of water, Hokage could use that water himself to attack.
*Mizukage can also liquify, but against Hokage that really is useless as well. Hokage controls water--he was not called the best water user of his time, he is called one of the greatest water users in all of history, which is a big difference--so if the Mizukage actually turned himself into water, he'd be screwed, completely at the Hokage's mercy. If he was water, Hokage could literally dismantle him, probably put him in a water bottle and end the fight, lol.
*Also, one small point, he doesn't have an instant transportation technique within the water. I can see where you're coming from on that point, but there's a difference between going into the water and coming up in a different spot and instantly teleporting. He cannot move quicker than FTG in the water, he just can't...
*IF they fought near a source of water, this fight could NOT be won based on Water Techniques. Even though i think Hokage's water techs are physically more powerful, Mizukage's Hozuki-type techs have unique enough properties that extra power wouldn't make a difference. On the other hand, Mizukage's water techs are physically way too weak to hurt Hokage except the finger-water-gun, cuz that can blast right through whoever it hits--but it would have to hit first. In the case of these two fighters, having a source of water nearby would give them an advantage only against someone else, not against each other. The fight would be won with different abilities. The Clam Genjutsu is indeed formidable and i could see Hokage having a hard time with that except he can use his finger on the ground to locate the real Clam and Mizukage, so i guess he actually wouldn't have that hard of a time. Also, if Hokage uses Edo Tensei... Mizukage would be completely screwed. Also, i don't see Joki boy as much of a threat... It's not very strong, just really fast and annoying and seeing as how it's mostly water, Hokage could probably stop it. Plus S/T techs are generally OP, so even though we don't know the extent of Hokage S/T use, I see Hokage winning 7 or 8 out of 10 times.
*But finally, if they were NOT near any water, there's not much to say. Hokage was so strong that he could use unimaginably powerful water techs with no water around. In this case, Hogake has the benefit of being able to use water as well as the rest of his arsenal. Mizukage would be screwed because all he has left is the Clam, which Hokage could locate with his finger. in these conditions, Hokage wins 10/10 times.
PLUS, with or without water, we don't know the extent of Hokage's S/T techs. So, with S/T Jutsu factored in, there's probably no way for the Mizukage to win at all....
So, while shit happens and there are always surprises and we don't know the full arsenal of either fighter--especially about Hokage's S/T jutsu--it is possible for either one to win. However, from what i've seen, read, and researched, I'd give it mostly to the Hokage