Colossus doesn't weigh 500lbs, he weighs almost 2 tons. Ergo 750 tons is not his limit, or anywhere near it if we go by that tons per square pound thing they did against the Nimrod's.
His weight has been brought up several times over the years, and it's always somewhere around a ton and a half, not 500lbs. That doesn't even make sense for a man composed entirely of a metal that resembles the densest metal known to man to weigh that little, when people like Hulk and Juggernaut weigh upwards of 800lbs.
If we said that a human of his size is about 240-250 lbs, that would mean his body has a volume of about four cubic feet; if his body has the density of steel, that would put his weight at about a ton (a little less, actually), whereas if his body is as dense as osmium he would weigh about 3 tons.
All of that's meaningless, however, since characters bringing up quantities doesn't count for anything...
Colossus is generally shown as being around Thing level in strength. That would make him 3 or 4 times as strong as Hogun - if Hogun's 35 ton strength level is accurate - which I doubt.
Anyway, Hogun is one of Asgard's greatest warriors, with thousands of years of experience fighting trolls, frost giants, etc. Colossus has a few years experience. He's just a kid compared to Hogun. Count in Hridgandr, and it's closer than you think.
I'd give a slight majority to Hogun.