For me I dont like the AM/PM schedules. They both do not fit my home life or life for that matter.
my UA bud is at the same senority as I am and he doesnt work before 0900 or after 2100. He has the ability to bid those trips. I do not. I never will. The only difference senority gives you at SW is week day or weekend. The most senior guy will fly as much as the most junior.