Take everything one day at a time. The only thing you should be worrying about right now is that next test in API (I guess that is your Navy version of academics?) Who knows, you may want to stay in after your ADSC. Don't pick the Poseidon just cause of the 737 type. Aren't there only like 10 of them anyways? Getting them is attainable but with that few of airframes, I bet they are gonna be competitive. Whats gonna happen if you don't get them? With the military, everything is fluid. You want to fly 737s in circles, but you may end up flying Greyhounds out to carriers. My .02 is pick the plane based off:

1. Mission/time you will actually spend in the cockpit
2. Bases
3. Plane with the best air conditioning