superhuman levels of strength, speed, durability and reflexes;
flight at subsonic speeds ;
several offensive weapons like concussive blasts of energy fired from his hands and optical sensors , plus an " encephalopathic ray " which places its victims in such a state of coma almost like death. The latter ray also allows Ultron to mesmerize and mentally control their victims , or implant subliminal hypnotic commands within their minds to be made at a later time .
Ultron also has the ability to convert electromagnetic radiation into electrical energy for use or storage.
Ultron has a genius intellect , an ability for creative intelligence and self- repair, superhuman cybernetic analysis skills and the ability to process information and make calculations with superhuman speed and accuracy. The expert is an expert in robotics and strategy.
The outer armor of Ultron is generally composed of Adamantium , which is almost immune to damage.
Most units Ultron are powered by a small nuclear furnace , and incorporate a " program transmitter " which can send some or all of the systems memory and personality of Ultron in other computer systems , or duplicate robotic bodies .
Ultron can also control other machines remotely.
Metallo's robotic body is very strong and highly resistant to physical damage.
Need not meet any human physiological function.
His brain is his only organic component is tightly protected in the head.
A well-known component of Metallo's kryptonite battery in your chest, giving you energy and defense against Superman. (Not usefull right now).
The only ways to disable Metallo (not kill) are shedding his head from the body or removing his battery power.
In recent versions, Metallo can adapt any machine within reach and integrate your own robotic mechanism allowing then recreate it from his own body.
Due to the fact that Ultron has more (and better) abilities, I think Ultron takes this win, also Ultron can control other machines while Metallo can only adapt to them, and Ultron does not requiere of red radiation or kriptonite like metallo.
Leave your opinion on who would win and why. Who would you like to have in the next hero battle?