Without going into specifics that meta tag is the starting point that enables you to create site consistency across all devices. That being said, there are different methods and uses of that meta tag which enable you to alter the site displayed in the viewport even further.
I would definitely suggest having a read of this: https://developer.mozilla.org/en-US/docs/Mobile/Viewport_meta_tag
To answer your question of whether there is an advantage or disadvantage. It was created to ensure consistency across most devices (advantage). In terms of disadvantages, well that comes down to your site and things like screen orientation bugs etc and this will require you to modify the meta tag to target certain devices. BUT those fixes will always require you to have that meta tag in place, so I would say, there are no disadvantages to that meta tag.