I Gaia vs DESI: Comparing Largest Star Maps Ever

[Hillwalker01]

TL;DR Summary

Comparison between star maps created by ESA's Gaia observatory and the Dark Energy Spectroscopic Instrument (DESI)

I've read that ESA's Gaia space observatory has created the "richest map of our galaxy (and beyond)" https://www.esa.int/Science_Explora...tes_richest_star_map_of_our_Galaxy_and_beyond

Meanwhile, it's been widely reported tat the "The Dark Energy Spectroscopic Instrument (DESI)" survey has constructed the "most comprehensive (or 'largest') map of the universe yet". E.g. https://www.wired.com/story/astrophysicists-release-the-biggest-map-of-the-universe-yet/

This isn't a "who's right?" or "which is better?" question ... I understand that these are very different instruments/surveys, using different methods, and no doubt have created very different types of 'map' (both incredibly impressive).

But can anyone give a layman's explanation of how these two surveys compare, how they differ, in what sense they can both lay claim to having produced the 'largest star map ever', how their data complement each other, and contribute differently to our understanding of the universe?

 

[Bandersnatch]

This is a very simple distinction, really.
GAIA looks at individual stars - mostly in our galaxy, but to lesser extent also in its closest neighbourhood. It's mapping the Milky Way.
DESI looks at galaxies, treated as individual objects (i.e. not resolved into component stars). It's mapping the large-scale universe.
In a way, it's like making the best map there is of a city, that doesn't concern itself with what lies beyond. And another best map there is of the globe, that doesn't have the resolution to zoom in on individual cities.