I boot up Windows 8 and the first thing I notice is that it allows you to login with your email credentials. Let's say if my laptop is stolen then what are the advantages or disadvantages of email based authentication?
Using the stolen laptop scenario; if you don't use whole disc encryption then all your data belongs to the thief. All of it. So what account you use is of little significance. Keep in mind, however, that if you connect your OS credentials with your email credentials then you're exposing a wider attack surface by which a bad guy can get them. Remember that email itself has no default assurance of security. Different systems implement email security in different ways and with varying degrees of success, but email itself isn't something you can really put a whole lot of trust in.
If you have whole disc encryption enabled then you're better off but I would not trust any security features to email integration. Yes it is convenient, but so is leaving the keys in the ignition.