I have used X01 and XX1 shifters and derailleurs for a couple years and found them to be very finicky. I could never get them to maintain smooth shifting. I had tried trouble shooting shifting issues that seemed to work for a bit, but still had issues eventually. AXS has been fit and forget.
Now being on AXS for about 6 months and shifting has been flawless. Even in horrible conditions, riding 6 days straight in pouring muddy rain soaked trails in Scotland. Everyone around me was having shifting issues here and there but AXS was perfect. Had an MTB 
that took over 17 hours, which the last hour consisted of thunderstorms. The mud was so thick I had to clear handfuls of mud between the tires and the frame. I oiled the chain the night before and didn’t reapply anything to the drivetrain over the course of this event yet never had a shifting problem.
So maybe I just had a lemon XO1 and XX1 mechanical equipment before, but for me I’m sold on AXS.