Asking about the difference between iron poles and concrete poles is like asking about the difference between houses built by laying hollow blocks and the one built by casting full concrete.
Before going into details lets discuss in brief what each component of the poles consist;
Iron poles are made of high-tensile steel or other types of steel material such that it can have the ability of withstanding the required load they will be subjected to when putting them to use, generally such poles are mainly used for structural erections where they are referred to as beams, of poles when their shape becomes cylindrical, beams can be H-Beam, V-Beam, T-Beam, and flat beam, etc. but poles can also be referred to as beams during structural erection in construction works, besides that; in general term any hollow or solid cylindrical beam or pipe can be referred to as pole when made to stand alone or against itself. Therefore iron pole is basically steel material made for the construction of materials in engineering while concrete poles are completely different from it both in material and functions.
Concrete poles are generally used in the connection and distribution of public electric lines, the reason is that it does not conduct electricity and therefore reduces the risks of electric shocks as a result of the power line having contact with the pole. The pole is usually made with solid concrete having iron rods lined up inside it to give it re-enforced strength, the iron rods are usually banded together with a quarter rod at distances not less than 8 feet along the length of the concrete before the mixed concrete is poured into the banded rods to form the pole, hence the concrete covers the pole walls thereby making the rods to be hidden inside.
However, there some iron pipes with a strong thickness which can be cut in pieces and used as poles for hanging things such as television antenna, cable, football pitch, and pillars for gates. But they are not used for electricity line distribution due to their conductivity property which makes the risk of electric shock very high. Meanwhile, in terms of strength under the same load capacity, iron poles are stronger than concrete poles.
Under exceeded load capacity, the iron pole will bend in the direction of the heavy load because of its malleable property, but under the same circumstances in concrete pole, it will crack and it pieces falling off remaining the rods inside which would have been deformed in shape towards the direction of the heavy load. The reason for such is because concretes are generally brittle.