First of all, this is only meant to be a comparison. I wouldn’t want them to fight but they’d be awesome fighting together. Despite being in separate comic book universes, Ironheart and Steel appear quite similar in their current incarnations, at least on the surface. They are both young, Black women with genius level intellects. They both fashioned their own suits of high-tech armor. They are both legacy heroes, inspired by other heroes that came before them whose abilities are similar. They are both relatively new to their respective comic universes in terms of coming out as superheroes. They both have great potential. I dare say that their most amazing and iconic adventures are in their future providing they are not killed off by some foolish writer.
Natasha Irons is Steel, a DC character. She is the niece of the John Henry Irons version of the hero Steel. In her original continuity her armor was built by her uncle and she donned it when he was incapacitated. At that time her intellect was no match for his but she was also a teenager at that time. Later on a quest for power she obtained a powers from an ill-fated project of Lex Luthor’s called the Everyman project. She briefly took the name Starlight but lost her powers soon after after Luthor removed them. As Starlight she had enhanced strength and endurance and could fly. She could also project bursts of light and create energy barriers. Later after losing those powers, as a side effect she gained the ability to turn into an intangible mist and fly and went by the code name Vaporlock. After that the new 52 happened many things changed. I am not sure her previous history is cannon. In current continuity she has built her own armor and her intellect rivals if not surpasses her uncle John. Her current armor has the usual expected capabilities granting her strength and flight. It also supposedly has the ability to grow to 60 feet tall though that last part may not be in current continuity.
Riri Williams is Ironheart, a Marvel character. By comparison this character is newer to her comicbook universe with much less backstory. Riri is named after her Father who died before she was born. She exhibited behavior problems very young possibly due to her extreme intelligence level. Her Mother fostered her abilities and made sure to provide emotional support. At 15 years old she created her own Ironman like armor in her college dorm room at MIT with materials stolen from the campus. She’s had a few mishaps along the way but she has become a competent and effective young hero. She has had help from Ironman and S.H.I.E.L.D. At the time of this writing she is a member of the Champions superhero group along with other noteworthy young heroes. She is considered to have a Super-genius level intellect as well as being a skilled inventor and Engineer. The abilities of her armor appear to be currently similar to that of Ironman. As of this writing she has new armor whose full capabilities have not yet been made known.