Don’t think anyone with an iPhone XS/Xs Max, X or Xr would downgrade to the pixel 3a, it’s not really meant to compete with the iPhones no matter what google is marketing.
Google tried to do the same thing with the original pixels targeting iPhone users, that didn’t work either.
“Pixel 3 buyers don't come from iPhone”
Who's buying Google's latest phone? A study suggests the most likely purchasers are Samsung owners.
https://www.zdnet.com/article/pixel-3-buyers-dont-come-from-iphone/
I believe the pixel 3a will not fare as well in sales as the pixel 3 has, it’s doa.
And the pixel 3 was a massive disappointment for google.