According to iCrew, the 7ER is junior in SEA (12069). 73N is 11811. Both will be tricky to get to quickly, though. Not sure a newhire will get the AE into the 73, then ALL those pilots will be seat locked for years (that's a big deal if you're trying to get in there). The consensus, too, is that the ER hiring will soon come to a halt.

You might want to focus on a plane/base that is the best commute initially. No sense in picking a SEA plane while living with a NYC/ATL commute. Or consider the other west bases -- LAX 73N plug is 12240 and SLC 320 is 12121 (and they are not new categories like the Sea 73N). 320 hiring will be slow thru the fall, then it will pick up for the 321 deliveries next year.