I guess I didn't even consider the argument in favor of Dobson - that we have a few really good offensive defensemen in the system, but we don't really have a prospect like Dobson, an all-round workhorse who could play both special teams and against opponents' top lines.
That said, at this point in the rebuild, you gotta go BPA, and when the choice is between two prospects picked within a few spots of eachother, I'll take the guy who's established himself as a top three defenseman on his team in two of the top five leagues in the world over the guy who has only proven himself in junior, all day every day.