The National is WAY bigger than the Expo. The Expo advertises 400 dealers, but in all seriousness, how many of those are dealers that you just walk past because you have no interest in cereal boxes and macaroni boxes? The National advertises "hundreds" of dealers but I can almost guarantee that many of those dealers have discount boxes that are better than a large percentage of dealers that set up at the Expo.
There isn't much hockey, but in my own experience, you'd be surprised at what you'd find if you ask dealers "do you have any hockey?". A lot of the time, I get a dealer breaking out a shoebox or monster box of hockey from under their table that they're selling at pennies on the dollar.
Chicago in 2017 and Cleveland in 2018...I'll see you there!