I recently bought a Mac for home computing.
Previously I owned an Alienware M17X R3. Beast of a machine - which I chose to buy over a Mac mostly because of gaming. I knew that the Alienware would be a much better gaming machine (obviously).
I did have work to consider - at the time I was doing a lot of general web development. Mostly using open source languages and tools. So I thought I was getting the most bang for my buck by sticking with a PC/Windows machine.
The weight, mostly.
My thoughts when first buying the laptop was that I wasn't really going to be using it on the sofa, on my lap; as a laptop! That changed when I got my own place and I wanted to spend my time downstairs rather than in an office room. Having one of those laptops on your knees for more than 15 minutes is really uncomfortable. The heat literally becomes unbearable.
A couple of years after buying it, I found I didn't play many games on it. I have a games console which feeds my gaming needs, from the comfort of the sofa.
When it comes to development, the Alienware was Windows like any other laptop. It was sporting a full HD 1080p 17.3 inch monitor, so I guess from that perspective it was a good dev machine.
Again.. Portability became an issue.
I fully believe that the main reason people buy a Mac is to own a Mac. People buy into the style. It's much cooler to own a Mac than a laptop running Windows.
Having said that, I can't deny that the Mac's style and quality had a part in my conversion.
When looking at price over performance alone, a PC will win every-time. So like I said, you kinda have to want a mac; to be persuaded by it.
Another note on the performance, Windows machines always seems to use more memory, suffer from more leaks, hangs and crashes than OSX. This is just from personal observation of course (I don't have any hard stats on this so I could still be wrong).
Working on a Mac
If I ever become interested in mobile app development in the future, I will need a Mac to support Apple products. It is very easy to run a Windows VM - if I ever require a Windows only application (such as Visual Studio, which to this day is by far the best IDE on the market).
Playing on a Mac
I've yet to try gaming on a Mac, as I said; I primarily use consoles for that now. However over the years I think the Mac is much more supported in the gaming world. More and more games are becoming available. With a service such as Steam, buying a game allows you to download and play any platform which that game supports. This has massively eased my transition to OSX from Windows.
OSX seems to be much more refined than Windows, right down to the little details. That sentiment not only applies to the OS, but also what Apple have achieved with the design of the Mac. I don't regret paying that extra for a well thought-out machine overall.