A very major difference. Non alloy steel "melts" at about
2400 deg F. any alloy of steel will tolorate much higher temps before failing. Non alloy steel loses about half its strength at around
1400 deg F.
Jet fuel ignites in regular air at about
410 deg F. With a concentration of oxygen it can burn much hotter. That did not occur in the trade centers. The only way to concentrate the oxygen would be to add it to the combustion by chemical proccess, preasurizing the combustion chamber as in tubocharging or fan compression or a direct infusion of pure oxygen. None of those proccesses were available.
I don't care how much you want to believe this or that theory. It was not physically possible for the jet fuel to weaken the steel enough to cause it to fail. Period!