Mike would have learned that solar system formation from a proto-planetary disk is not just the favorite model, but finding strong fresh support from study of the Orion nebula. Nobody who matters believes in the solar fission model he prefers.
Hoagland would have been interested in some very fine artwork showing that the asteroid 25143 Itokawa is a loose accretion of material that's as much as 40% void. He might recall saying emphatically, when discussing Phobos, that "you can't have a natural object that's 30% hollow."
They both would have learned that, although a Van Flandern-style massive impact on Mars is indeed possible, even likely, such events were not at all uncommon in the early solar system, and that all four of the rocky planets almost certainly experienced the same catastrophic fender-benders.
Hoagland would have been disappointed that nobody credited him with being the first to publish the possibility of life under the surface of Europa, one of his oft-repeated claims. That's because the claim is a lie. Maybe he'd also have been chastened to discover that the volcanoes of Io are not in any way grouped at 19.5° latitude, as he has falsely claimed.
I guess they'd both have been disappointed that nobody mentioned cities in the rings of Saturn, monument-building civilizations on Mars, or robot heads on the Moon. My God, these people didn't even mention 19.5 once. Clearly a cover-up by TPTB.