Tony has the capability to create armor which incorporates magic [eg. the Thorbuster]. He just doesn't utilize that type of thing as his 'every day driver', like Doom does.
Removing the people inside, if I needed an armor i'd choose Iron Man. It seems like he has focused on the armor and even though he'd lose in a fight he's all about the armor.
The only time Doom and Tony haven't stalemated when they've fought that I can recall, is fairly recently when Doom emplored the magical Crimson Bands against him - [you know, the battle where Sentry ended up owning Doom to the nth degree (lolz)].
afaic, Doom's armor is only 'superior' because it incorporates magic.
Like I said though, the instances where Tony and Doom have battled always resulted in a stalemate [unless Doom uses magic] iirc. Hell, in one of their first battles, they were both BFR'd to a distant timeline, and actually had to combine their knowledge/tech to return home [neither could have done it alone].
In a recent Mighty Avenger's comic, wasnt Doom trying to figure out why Iron Man's armor is so amped up recently?
Also i wouldnt say Sentry owned him. He teleported him behind him when he wasnt ready and basically cheapshotted him. Teleport me in behind a lot of Marvel characters who arent ready for it with a shotgun and I'd "own" them.
Before that, when Doom was first using the crimson bands against Tony, Sentry charged him head on and punched the shit out of him. Then they were all teleported to a different dimension, via Doom's tech.
But Sentry cheapshotted Doom there as well, while he was talking to Tony. And to be fair, Doom's magic pretty much had Sentry downed in that first encounter despite Sentry getting the the first punch in.