Do you care about the way things look, and does that mean you love the idea of having Apple hardware in your studio? If so, go Mac. If not, go PC. They are more affordable, more customisable, and the only advantage Mac has is Logic, which is great, but then so are Cubase and Reaper, both of which are cross-platform.
Well.... I think the differences between Windows and Mac go much deeper than just the looks of the computers. As noted above, I worked on both types of set ups for years when I had a day job in a studio using Macs on top of moonlighting out of my own studio which had a PC. Both machines were fairly equal in stats but the Macs blew away the PCs I had.
Some people sneer at those that like the good looks of Apple hardware but I think the appearance of your equipment can make a massive difference to your frame of mind. My setup looks remarkably easy to tinker around with, and guess what, I spend hours of my life tinkering and customising and it doesn't help my music making in the least. But I'm a geek and I enjoy it.
Your work space is, indeed, very influencial in how you work. I'd say it's less about which type of computer you have and more about how you set up your studio and space. Some people flourish in dark or messy spaces while others shine in light(er) or clean studios. To each their own!