I think it's fair to say that Apple Silicon makes for incredible laptops, given that it excels in performance per watt. They cost a lot of money, but given the excellent performance, battery life, screens and general build quality, you get a lot too. The only downsides are the much-noted price of memory and storage upgrades, and well as being almost impossible to repair by anyone other than Apple (again... $$$). Yes AppleCare, but aside from being a further expense, second-hand purchases without AC will be risky (which will surely affect resale value).
The desktop is less convincing, when you take into account the PC you could buy (and especially, build) for the cost of a Studio Ultra. It also lets you scale in the way that best suits your needs e.g. a 1x M3 Max-level CPU + a 2x Ultra-level GPU. Apple can only scale in whole Max-sized chunks (and then, only up to 2x Max).
The issue with big iron is likely a) the limited parallelisation of most software, and b) higher core counts tend to mean lower clock speeds. I'm not up on M3 benchmarks, but a quick Google turned up this analysis by Tom's Hardware, which reckons the M3 Max is about level with a 14900K in GB6 single and multicore: https://www.tomshardware.com/pc-com...it-405-ghz-challenge-raptor-lake-in-geekbench. Impressive given the much lower power draw, but as the K is 'just' a 24 core chip, there's no real reason to be comparing the M3 Ultra to 56-96 core x86 processors, which as you point out, are highly specialised for very parallel (and likely multi-user) workloads. The 14900K is also just a refreshed 13900K; Arrow Lake (and Zen 5) should bring greater advances on the x86 side.
The desktop is less convincing, when you take into account the PC you could buy (and especially, build) for the cost of a Studio Ultra. It also lets you scale in the way that best suits your needs e.g. a 1x M3 Max-level CPU + a 2x Ultra-level GPU. Apple can only scale in whole Max-sized chunks (and then, only up to 2x Max).
The issue with big iron is likely a) the limited parallelisation of most software, and b) higher core counts tend to mean lower clock speeds. I'm not up on M3 benchmarks, but a quick Google turned up this analysis by Tom's Hardware, which reckons the M3 Max is about level with a 14900K in GB6 single and multicore: https://www.tomshardware.com/pc-com...it-405-ghz-challenge-raptor-lake-in-geekbench. Impressive given the much lower power draw, but as the K is 'just' a 24 core chip, there's no real reason to be comparing the M3 Ultra to 56-96 core x86 processors, which as you point out, are highly specialised for very parallel (and likely multi-user) workloads. The 14900K is also just a refreshed 13900K; Arrow Lake (and Zen 5) should bring greater advances on the x86 side.