What advanced metrics are we even talking about? PFF has always had Armstead raked higher, even in 2019, but there isn’t a person on this earth that would say he was the better player that season:
Meanwhile the advanced stats from Football Outsiders has DeFo better across the board.
I’ll also admit I don’t love going to advanced stats. There’s an advanced stat for anything to make your argument look “good”. IMO DeFo >>> Armstead, and DeFo is the reason AA had his one great season.