The industry standard is becoming Centerlock, mainly because Shimano want it to. As stated elsewhere on the thread, 6-bolt was the original standard, however Shimano then launched their own standard - Centerlock. They own the patent: https://patents.google.com/...t/US20070240945A1/en
As a result, Shimano are incentivised to ensure that the industry moves across to CL, something they've actively encouraged by only offering their high-end (Ultegra / Dura Ace) level rotors in CL, not 6-bolt. Given they're by far & away the leading OE supplier of road groupsets, hub manufacturers have been forced to switch to CL.
Interestingly, the graphic below shows why 6-bolt is arguably the superior design from a hub designers perspective - you can increase the bearing spacing on the axle as shown. However, it undeniable that CL is far superior from a user perspective when fitting, aligning & changing rotors.
Edit: can't get the graphic to work, link here: https://ibb.co/WKPLpfT
yes, shimano wants their product to become the industry standard. zipp wants their driver body to become industry standard. i want the slowtwitch forum to become the industry standard. i'm not arguing whether it should be, i'm just arguing that centerlock is
now the industry standard. as for which one is the better design, i don't feel a difference in the braking, and i've never had a centerlock hub fail, so the utility of the design (for me) now flows down to other things. if you've stripped a bolt head from a 6-bolt system while taking your rotors off (i have) when packing your bike for airline travel, you're somewhere between inconvenienced and screwed. hence centerlock (for me). i think your post recognizes the utility of centerlock for things like this (e.g., changing rotors).