Obviously, everyone has different priorities and resources. If my clients paid for my flights, I would fly First Class and accrue big miles on American.
But really, my biggest pro for WN are the CP, ability to change or cancel, and free bags. I will not pay for BS as often there are no "preferred" seats anyway. And the rest are all the same. Of course, if clients paid, ......
I agree WN needs to get scheduling better. Add 5 min to turnaround. Get people on board (and off) faster. Start boarding earlier. And for some reason, plane sits 10 min after boarding complete? Used to be a rush, not now. With short turnarounds, they just keep falling further behind all day.