A Mac Pro (2019) - I was/am using the 2019 Macbook Pro, but under heavy load (compiling rust/flutter mostly) the machine would get slower and slower as it became more and more heat saturated, and worse, when driving an external monitor the GPU would get hot as well and the whole UI becomes slow.

The mac pro is ~2.5x as fast in compilation but more importantly it doesn't lose responsiveness when the CPU is fully loaded, so I can still browse the web while waiting :D

EDIT: I said 2016 MacBook but it's the 2019 16" (2.3 GHz/8Core/i9) and to be clear, I know the 8-core Mac Pro on paper, has faster clocks, but it's surprising how much of a difference the thermal headroom makes to responsiveness and productivity