A vise is a vise, right?
Well actually, metallurgy has come a long way in the last hundred years.
Most vintage vises were made of Gray Iron; we now have ductile iron, Austempered Ductile Iron (ADI) and Forged steel vises.
Forging processes did exist at the turn of the century, but there really was no profitable way to forge something in the shape a vise. Making vises out of forged materials required welding various pieces; and welding didn’t become widely accessible until after the 1940’s.
Vintage vises are great, they come from a time when it wasn’t so much about calculating how strong something needed to be, but rather overbuilding to the point where it really didn’t matter anymore.
Even so in metallurgy forged steel is substantially stronger than cast steel, let alone cast iron.
Ductile Iron and ADI are modern takes on Gray Iron which makes iron flexible in cast-able form, with many of the same properties as steel but at 70% of the cost. Cost aside, ADI and Ductile Iron certainly still don’t compare with forged tool steel.
The best modern forged vise I have used (and own) is the Ridgid series vises. They are also sometimes sold under the Peddinghaus name.