Perhaps with your boat this will have no bearing, but both wire and rod exhibit a fatal flaw.
They are impossible to hold on to if you need the bobstay to get back aboard should you find yourself in the water unexpectantly.
Yes, the rod is better than wire, having a swedge fitting on a wire end that is constantly immersed in salt water is asking for failure, it's not debatable.
In boats with bobstays the most common cause of rig failure is bobstay failure, and the most common place of bobstay failure is the lower swedge fitting.
If the boat can use it, the best is heavy chain.
Any compromised links are readily seen, it has an elasticity that absorbs intermittent shock loading, and perhaps the most important feature: If you are in the water, you can hold on to it to save your life and pull yourself out.