Verifying an account with SMS as opposed to email address

In order to be more secure we're looking into account verification. The two options are:

  1. Email address verification (Asking the user to click a link in an email sent to their account to verify the account)
  2. SMS verification (Asking the user to enter 4 numbers sent to their mobile into a form on the screen)

For me, I much prefer the SMS approach. Here's why:

  • I don't have to leave the interface.
  • It's quicker than opening/authenticating your email client.
  • From a security perspective, it's much harder to create a 'fake' phone number than it is a 'fake' email account.
  • If I'm using a laptop, when it's email verification, I usually use my phone to open the email and click the link. Then I have to go back to the laptop and refresh or navigate somewhere.

So does using SMS verification without email verification make sense from both a usability and security perspective?

Are there any valid reasons why a user couldn't receive an SMS message in order to complete their registration?