You know, I think one of the things that I personally would have to consider is pleasure.
I have always used Macs. Like, since the 80s. I have always strongly preferred them. I have, however, only bought a Mac a couple of times. The rest have been computers or laptops that my work has furnished. The last time I bought one myself was in the late 1990s.
Right now, I have a Mac at work and use our (my husband bought it) PC at home. I have finally become proficient on the PC (it took a while), but I get no pleasure at all out of using it. It's a tool. It often frustrates me, and I often hate it. But it gets the job done.
If I had to buy a computer that I was going to use all the time, like if I was self-employed and heavily reliant on a computer that I'd be using 8 hours a day, I think I would really struggle with this decision. As it is now, I don't mind using the PC for bill paying, surfing the Net, etc. I have even written full-time on it for six months or so (while I was on a sabbatical from my job). While I was doing that, though, an almost-daily refrain from me was, "If I decide to quit my job and write permanently, screw this, I'm getting a Mac." I haven't quit my job yet, but if I did, I think that I'd strongly lean in that direction.
So, you probably have to think about what the tipping point is for you, where the amount of time you spend on the Mac justifies the extra comfort of having a more expensive machine.