Hey, that was me 20+ years ago. What a deal.... using the military to gear you up for the airlines! No one has the crystal ball. Lot's of good advices here. Study hard, chair fly, play hard, and don't **** off anyone (especially the IPs).
As for type of aircraft, definitely no helos if you want to land a job with the majors right away after your 10+ years bending over for Uncle Sam. Fly what you want, if you have a choice. Don't listen to these guys who'll tell you that the airlines prefer heavy pilots; that's ancient history. You are going to be Uncle Sam's beeeeeatch for 10+ years so you might as well fly what you want, given the choice. Every MWS has its pros and cons. Kick a$$ in SUPT so you'll have a choice! Good luck.