Lex Luthor seems to be getting a scientific push again -- Lexor is about to be back, he's working with Brainiac, he cured an incurable disease in the space of an hour or so, and I suspect we'll be seeing even more scientific craziness from his 10 issue mega arc in Action Comics by Paul Cornell.
But thus far, his scientific feats are few and far between, and no where near the frequency and level of Tony Stark's best. So Stark wins.
The battle armor he had wasn't built by him, but by Apokolips, by the way. And he had a force field covering his head. By that same token, Brainiac 5 would have to be an idiot, since all he's got his a full body forcefield. 🙂