Mostly payload and Airborne time.
Idk what is the current status of Zephyr (google search suggests 26 days?) but Loon balloons were consistently reaching 300 days of airborne time.
Thanks for the link. Pretty impressive mission despite the unfortunate ending!
Edit: Did it actually crash? The article says it was “brought down” but that could have still been a glide and regular landing if it lost power.
https://newatlas.com/aircraft/zephyr-8-mission-ends-abruptly...
Unfortunately, it ended with a crash.