Semi-annual blogger Derek Sarley:
VOA is a measure of how well a team has played and DVOA corrects for opponents, so you can throw out any concerns about strength of schedule and say things like “DVOA proves the Eagles have the league’s twelfth-best defense, even if you claim they didn’t play very many teams that were any good.”
Except you can’t. DVOA says nothing of the kind, as we can best demonstrate with a couple of charts. Here’s the first one, plotting this season’s DVOAs against VOAs:
Long story short, opponent adjustments are nice, especially for comparing teams quickly. But DVOA and its ilk will never be able to provide a complete understanding of a single team or unit. Even advanced stats need context.