That is one major advantage to OS X. You can make a drive image and boot off of it. Helps for migration testing and backups. It really frosts me that Microsoft hasn't figured out how to do that yet. I can keep a 128 GB flash drive in my bike bag and restore my laptop anywhere in the world I can get a new HD. Pretty damned convenient.
I love the fact that the included OSX backup (and dead simple) program Time Machine, creates a bootable USB backup - there's nothing remotely similar in Windows land but should be.