Yes. The Pixel 3a is larger than the Pixel XL.
I have large hands, and the OG Pixel is the largest screen I can fully use one-handed comfortably. I've used the OG Pixel XL for about 3 months now (because I already had one when my OG Pixel died, RIP) and I still hate the size.
Aside: the screen on all the Pixel 3a display models I've checked out the past few months (I keep getting tempted to finally buy one but) is tinted yellow and has serious burn in issues.
This makes me wonder if there is a way to customize Android's screen resolution so the top of the phone is just ignored (I don't mind if my phone has a large bezel, chin, or forehead).