The flow is insurance of attrition of very senior captains, it's really nice in that way no matter how you feel about the "guaranteed AA job" its advertised as.

I'd probably interview at Endeavor if you are into the east coast before you commit to anything. The main issue with Endeavor is that you'll be waiting a long time for a class date after you interview, not a problem for you since you still have time to build. Not saying they're definitely better than Envoy, but a conditional offer from them will really help you consider one from Envoy in a balanced way.