It’s simple really. If you’re comfortable with technology, at home with a screw diver, prepared to do some research and able to cope with the odd surprise or two, then building your own PC is a lot cheaper.
Can’t say much about the MAC. Never been able to afford one that could compete, performance wise, with a PC I could build my self.
Had some airy moments though, like having to wait weeks to get a bad cap replaced on a Gigabyte Mother Board under guarantee.
Edit: Also, had a beauty with the last build before this one. The PC would boot, run for a while the intermittently turn itself off and reboot. Ended up being a faulty reset button. On a brand new case too.
Not trying to put you off or anything 