There’s a fairly significant performance difference between Apple’s new cores and the Pi 4’s A72s.
If you ignore that and the high-end display, touchpad, and keyboard, then I suppose it’s not too far off from a Pi in a fancy case, but then you could say the same for any laptop.
In 2012, the same Mac mini case held a cooling system for a 45W chip, 2x2.5" storage bays (or one storage bay and a DVD-Drive), 2 RAM slots, and had three more ports and a card reader. They really used every last corner.
None of these new M1 devices will be densely packed. They’re putting smaller boards into the same enclosures. I assume next gen is when they will take advantage of space savings.
My 2012 Macbook Pro was also slowly dying. As a Hail Mary I opened it up, cleaned it and renewed the thermal paste on CPU and GPU. Now it's back to old speeds!
If you ignore that and the high-end display, touchpad, and keyboard, then I suppose it’s not too far off from a Pi in a fancy case, but then you could say the same for any laptop.