I have switched from Mac to Sony and from Sony to Mac. I currently own a Sony Vaio and a Macbook.
I had a 2008 macbook for 1year. Never a problem.
Then I went to a 2009 Sony Vaio. After 2 years, Windows crashed and I need to reset Sony to factory condition. After 1 month, crashed again. After restating it once again, I decided to dual-boot with Linux. After a few months, Windows disapeared and I can only enter Linux now. And recently, If I run any intensive task, the computer shuts down automatically. Its still good for surfing the web.
Ive now been again on a macbook for 1 year, still not a problem, but who knows, I neer owned a Macbook more then 1 year.
I recomend both, get the one you think is more good looking. In terms of OS X vs Windows, I think OS X is way superior, specially for notebooks where you use a lot of the trackpad.