I’m trying to learn more about why Select By Location performs better than spatial SQL queries.
Why are spatial SQL queries so much slower than Select By Location?
In a related post, a commenter suggests:
[Your desktop mapping application] may use graphic card hardware acceleration to solve the problem, so you may be comparing apples to oranges.
https://stackoverflow.com/posts/comments/133894626?noredirect=1
Does Select By Location in ArcGIS Pro use graphic card acceleration?
Possibly - my GPU jumped from 6% to 27% for a split second doing a spatial selection. But there may be other things (spatial indexes, topology, reprojections) that help GIS with geographic/graphic queries.