OSX is great (Barring a few things I hate about it, but I hate things about all the operating systems.), but personally I settle for windows/linux boxes for my workstations simply due to the price and performance. I can't be bothered to deal with the headaches and weird gotchas that I've seen popup on Hackintoshes, and I'm not nearly rich enough to indulge Apple in their delusions of what their hardware is worth at the upper end.
My daily general use computer for email, web browsing, and other light workload things is a MacBook pro, but the workstation I sit down to do serious number crunching at is a Windows 10 machine. And I use a digital KM switch to link the two together so I can readily enjoy the useful aspects of both.
As for iMac systems, I simply don't trust them enough for use as a development/work rig. If something dies on it, pretty much the entire thing goes out the door while I wait for servicing. If something dies on my work station, then it is trivial to pop the case open and swap things out and 'make do' with bits of older hardware from the storage bin while I wait for proper replacements. Give up my entire computer because of a blown backlight in the monitor? ... No thanks.
I really hope that Apple decides they still want to actually compete in the production work station market rather than coast on fanboyism, and bring back a proper workstation tower design with a focus on off the shelf parts, and being able to store your drives and such in a case rather than external enclosures.