I agree it depends on your intended usage, but disagree on most of everything else the other poster said.
Apple systems are a bit pricey, BUT they're quite the rugged little beasts beneath the pretty exterior. Apple doesn't cut corners in the manufacturing process the same way other computer makers do, which really is the source of most Windows problems. Windows doesn't like shoddy hardware, no OS does, but Windows is especially prone to breaking when the hardware quality is low. It's why I won't go near HP/Compaq systems unless they're basically given to me. To be perfectly honest, I have never seen any system that can take the kind of abuse Apple systems can, and keep on running.
I would say that Apple systems are really no more overpriced than any other comparable system. Lenovo is the laptop maker that tends to be the only one close to nipping at the heels of Apple on quality, and their systems are pretty comparable in price. Quality costs money, it's that simple.
All that aside, there's something else to consider, and that's the operating system. Apple systems have the option of running OS X. Put simply, for the past couple of years OS X has been what Microsoft wishes Vista could have been. Half the ideas for Vista are copied directly from OS X. When it comes to a desktop OS, you simply cannot beat OS X. However, it's not for everyone, it does require a little adjusting, and you have to replace almost every one of your favorite Windows apps.
On the other hand, the Sony system sticks you with Vista, and good luck trying to find all the drivers you'd need to make XP work on it. If you don't like Vista, your only other real option is Linux, which doesn't always work so well on newer hardware.
You DO have the option of dual booting Windows with Apple systems. You can even buy programs that let you run Windows programs on OS X with very little performance hit.
If it were me, I'd go with the Apple system. Better construction, you'll have a much better chance of getting XP to run on it if you don't like OS X, and you really get the best of both worlds -- OS X and Windows -- with the Apple system. It will hold its value a lot longer if you ever decide you want to sell it, it'll weather the daily life of a laptop considerably better, and OS X really just is flat out a better desktop OS than Vista.