The more Scarebuses I fly, the more I've started to gravitate towards them; better cabin experience, IMO. That said, I have not yet flown on a 787 or a 737 MAX, but Delta seems to have clearly made the decision to move away from Boeing for the foreseeable future. The A350s are coming in this fall (farewell Northwest 747s), then the Bombardier CS100/300s starting next year (finally phasing out those ancient MD-88s), and the A330neo starting in 2019 (phasing out older 767s).
I'm sure Boeing will cry about undercutting and unfair trade (they already filed a complaint over Bombardier's pricing earlier this year), but they've done that so often in the past 20-25 years, that eventually it gets to be like the boy who cried wolf. American and United seem to have no problem continuing to order planes from them, and we all know Southwest is a "Forever 737" airline, so...