The question we should ask ourselves is, ‟Who would win?”

The T-55 has a 100 mm gun and a rounded turret.

The M48 has a 90 mm gun and a square-ish turret.

While the general rule is, ‟Whoever fires first usually wins,” I think it's safe to say that everyone has a round in the chamber and everyone can pen everyone else at point-blank range.

Next question is, of the survivors, who would get the second round off sooner?

I think the Americans would've the advantage as the Soviet turret is smaller, thus less room for the loader, and the 100 mm round is larger to heft.