Under 20% seniority there isn't much of a difference if any. Above 20% can see more days off because the 737 Caribbean day trips that go to the top 20% are more productive. Yes, the 321 will show up one day and the bus will also be a growth fleet, but those trips will go senior. If you can't get EWR 737 out of BI just bid any 737 and you will get EWR in the next vacancy.