Sibley's seems the choice for professionals and highly experienced amateurs. It uses technical jargon in places.
NG, Peterson, or Audubon are good for beginners.
I don't like the layout of the Audubon. The photos and text are in different sections of the book and require flipping back and forth. Cumbersome when trying to ID a bird that is flitting around and you are trying to keep an eye on it.
The various cell phone apps require at least cell service, preferably a wifi connection. Don't work out in the boonies when you need it most.