iPhone 11 Pro Max's Geekbench multi-core score is ~3300. An 8-core MacBook Pro's Geekbench multi-core score is ~6700.

Now imagine the iPhone's CPU with double the cores and a giant heatsink + fan. I bet it would double maybe even triple a maxed out MacBook's score.

On the other hand, most software does not utilize ARM's NEON instructions (counterpart to x86 AVX). In my tests [1], H.265 software encoding was 3.5 slower on ARM than on x86 in terms of frames encoded per watt of energy consumed.

[1] https://quanticdev.com/articles/h265-encoding-on-arm-cpus