The 220 and 717 are the least desirable planes right now just due to their limited bases. Some people are also wanting to avoid the slightly lower year 2 pay. If you live where those fleets are based then you’re ok but a new hire could definitely be stuck with a crappy commute for 12+ months if they are towards the bottom of their class seniority. I guess the 7ER is also more limited as well. Right now the 320 and 737 are in every base (until BOS as 320 only) and thus offer the maximum flexibility if you can’t hold your desired base on the initial drop.