Dropped Windows over a decade ago.
Too glitchy, too prone to viruses and malware,spent too much time repairing mine and then all my friends` machines.
Apple, for now. Apple`s big suck is they make it so you cannot install any new OS into an old Apple product unless you do a semi-complicated hack to force it to accept.
Depends on what you define as old - 8 year old machines (and in some cases older) can still run the latest version of OS X. Try installing Windows 10 on a mainstream PC that old and watch the “fun” you get.
Usually - not always, but usually - Apple has a good reason for their model breaks for new OSes, often, “The older hardware could run it, but the user experience is really going to suck.”