It has the greatest light-gathering ability (product of field of view * aperture) of any telescope yet. That's the key figure of merit for a surveying telescope! (As I understand—I'm not a domain expert).
- "Combined with its large aperture (and thus light-collecting ability), this will give it a spectacularly large etendue of 319 m²⋅degree².[6] This is more than three times the etendue of the largest-view existing telescopes, the Subaru Telescope with its Hyper Suprime Camera[36] and Pan-STARRS, and more than an order of magnitude better than most large telescopes.[37]"
- "Combined with its large aperture (and thus light-collecting ability), this will give it a spectacularly large etendue of 319 m²⋅degree².[6] This is more than three times the etendue of the largest-view existing telescopes, the Subaru Telescope with its Hyper Suprime Camera[36] and Pan-STARRS, and more than an order of magnitude better than most large telescopes.[37]"
https://en.wikipedia.org/wiki/Vera_C._Rubin_Observatory