We have this conversation every year or so here. When HSR first launched, there was much excitement about it because schedules were predictable and many of us had awful experiences flying. But, now that the PLA has been bounced out of the major flight corridors, flying is much better than it was circa 2010. I used to keep track of my door-to-door times on BJ-SH. As long as you don't go to the airport super early, flying is usually a clear winner. That calculus changes when you look at shorter distances (e.g. Shanghai-Xuzhou which is the midpoint of the Jinghu Line). For Beijing-Xi'an, I prefer flying, not because it's materially faster, but because the experience is more civilized IMO (i.e. no need to deal with crowded train stations, dragging luggage vast distances, or going without real food for 4+ hours).