I don't remember reading anything that definitively states that. I guess it partly depends on what Ultimate stories are in cannon. The two Iron Man minis written by Ellis in the infancy of the Ultimate U say that Ultimate Stark's entire skin is brain material or some nonsense. You could argue that would make him smarter than his 616 counterpart. But those minis aren't referenced again so it's anyone's guess...
I really enjoyed that mini-series, and it gave Ultimate Stark a really interesting back-story. Shame they didn't run with it. I remember reading somewhere that it was basically removed from canon.
In the end, I think Ultimate Stark turned out to be very similar to the 616 version. I haven't really seen anything to indicate he's any smarter. Certainly the Iron Man models in 616 seem more technologically advanced.