You don't want more pixels, you want better pixels, optics and positioning.
I would think the M1s are more than fast enough to do a nice job downsampling in real time from 4K to 1080p.
Also, the M1s are fast enough to be someone's main computer for a long, long time. 4K future proofs your system a little more.
A lot of Youtubers are not streaming, which is what most people use their laptop webcams for.
> I would think the M1s are more than fast enough to do a nice job downsampling in real time from 4K to 1080p.
Just video encoding a 1080p stream in itself is already extremely intensive even for high-end CPUs. Especially considering that I (like most users) am simply trying to take a call, and have actual work already going on that I want my processor to spend its time on.
4K downsampled to 1080p looks a lot better than a 1080p "native" sensor.