There are some differences between the 9a and 10a that might influence purchase decisions. Tom's Hardware did a side-by-side of the Pixel 9a vs 10a (albeit not running GrapheneOS):
https://www.tomsguide.com/phones/google-pixel-phones/pixel-1...
https://www.tomsguide.com/phones/google-pixel-phones/pixel-1...
This leads to substantially better battery time (which can be seen in the review) and connectivity.