Personally I think Windows/Intel is better.
Fair enough... but do you say this based on familiarity with both platforms, or are you just saying Windows/Intel is better because you've never used a modern OSX/Intel Mac for any length of time?
Not being a smart-ass here, but in my experience those who express a strong preference for Windows are almost without exception people who haven't spent more than 2 minutes using a Mac in the last decade. The people I know who have been exposed to both platforms and understand them both, without exception prefer Apple and MacOS. I don't say this as a way of saying "see, you're wrong," but as a way of saying to those who really haven't investigated the platform that they should consider there might be something they're missing.
Can you do that in the Mac? I don't think you have that much flexibility.
Building machines from scratch? No, Apple's whole plan is that you buy a machine entirely designed by Apple, and since the motherboard and the CPU and the video card and the RAM and the OS are all standard Apple stuff, the system just works without any BIOS tweaks or firmware flashes or other hacks.
If you're a hobbyist who just likes that kind of "under the hood" stuff, there's nothing wrong with that. Some people like American muscle cars because it's so easy to get under the hood and play around... but recommending a '67 Camaro to someone who just wants a reliable commuter car is a bad recommendation, and likewise recommending a hot-rodded, self-built, tweaked and overclocked PC to a person who wants a reliable tool for getting their work done, is a poor recommendation.
But again, for those individuals who love tweaking and manipulating, and seeing how far you can overclock your liquid-cooled CPU without frying it, then for sure the Windows/Intel platform is the best way to go.