Good article again!
To me, going on this and other bits I've read, it seems that, despite being a bit of a useless so-and-so work-wise, Arneson invented or popularized what, to me, to groups I've played in, is what we really enjoyed about RPGs, and which was broadly applicable to multiple RPGs, which is a certain approach to DMing, to world-building, and so on, and it's one that EGG has both railed against in unequivocal terms, and also sort of seemed to almost-agree-with at others. In general though EGG has given the impression that his ideas re: how D&D and DMs should be were far narrower and even slightly repulsive to most people who run RPGs (including a lot of OSR people) - I mean, the less said about Role-playing Mastery the better. They say "Never meet your heroes" which is probably good advice (though I was behind Sigourney Weaver in a queue at a bookshop once and nothing bad happened except her smiling bodyguard looked at me in a "Don't try and ask for autograph, bro" way), and nothing disillusioned me about Gygax as hard as that book. I read it at 13 and I was already too sensible and too experienced as a DM for it. Awful.