What are the differences in their games? Both decent skaters for their size. Both liked to use their size down low. Both players you wish would play meaner and use their body even more. Similar pass/shoot ratio. Similar production. Both can get caught not engaging enough defensively. And as you said, similar size. Heck, even their draft position is oh so close.
I see a lot of similarities, so what are the differences? Ones russian and ones a canadian/american hybrid. what else?
Back when Antropov was drafted, one of the bigger concerns was his skating, and that's back when skating wasn't as big of an issue. Brown's skating is typically described as an asset, with the caveat, for his size.
Edit: It's worth pointing out that Brown is still viewed in the "what he could become" lens, where as Antripov can be viewed as what he became.
Brown has a higher upside than what Antripov became, but so did Antripov. Another example is a guy like Colborne. He was also seen as a bust or boom prospect, much like Brown, and Antripove, but he fell closer to the bust end of the spectrum.
Antripov
Assets: Physical, vision/hockey sense, + passing.
Flaws: Lacks acceleration and speed, shot needs improvement
Colborne
Assets: Soft hands, size/strength, +passer, good skater for his size
Flaws: Work ethic. Not physical (particularly given his size)
Brown
Assets: Skating (for his size) powerfull stride and good edgework (for his size), vision, passing. Puck protection. Good shot
Flaws: Work ethic, needs to use his shot more to be less predictable.
All three are similar and all three were/are seen as potential first line centers, but all three had aspects of risk associated with their development.