Whatever is in NYC is typically most junior of course. Historically the A220 (or DTW717) would be more junior due to lower pay and limited bases, with 737/A320 more senior and 7ER the most senior. It is always hard to say though, as a lot depends on which base/fleet combinations are available in any particular class. NYC7ER has gone the most junior in numerous classes this year, and that may continue with the number of bases shrinking and fleet retirements on the horizon.