Is it true wrought iron or powder coated steel in wrought iron style (most modern fences are made like this as we have found in our research)? True wrought iron is very expensive but very durable. Powder coated steel if scratched will rust, so a lot of upkeep. Aluminum is not as durable as steel. Vinyl is much less maintenance and will actually last much longer than metal, because it will not rust or rot.
That said many people in our neighborhood have had vinyl for almost 20 years and looks like new. They power wash it every spring. Some of the larger estates near us actually have the true wrought iron gate with stone fencing with still looks great. The few homes near me that have the powder coated steel fencing/gates are showing lots of rust.