Plasma Cutting is a lot more versatile than oxy fuel cutting because plasma cutters are not limited by why type of material can be cut. Carbon steel, stainless steel, nickel, aluminum, magnesium, titanium, cobalt, brass, and copper can all be cut using a plasma cutter.
Thickness is a plasma cutters main limitation. It takes a heavy duty plasma cutter to cut 1 inch and greater thick material.
An Oxy Fuel torch is limited by material type. Pretty much only carbon steel can be cut.
most any oxyfuel torch (aka oxy-acetylene, or gas cutting torch) can cut steel thicker than 1 inch as long as the tip size is right and tanks are big enough.