The creator of fff.nvim[0], Dmitriy Kovalenko, had an interesting analysis of this on Xitter[1]. The TL;DR of this is that Anysphere/Cursor is being somewhat disingenuous and does not include the index-creation and recreation time in the comparison nor do they include the CPU or memory overhead, where rg (and his tool, fff.nvim) are indexless.
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0: https://github.com/dmtrKovalenko/fff.nvim
1: http://x.com/i/article/2036558670528651264