Samsung 670 would be slower than a flagship, and you can always get flagships on sale after a couple months for upto 1/2 off. Not sure the pixel is worth the money.

Pixel 3a also lacks the Pixel Visual Core that shipped in Pixel 2 and 3, which also may explain some of the discrepancy.

I though that only affects processing time, not the end result.

Some features are Visual Core exclusive I think, so it depends on what you're trying to shoot.