Pros:
One google account for all google products including google+, google drive, android play store, etc.
Google account is universal. You can sign in into a lot of websites using just your gmail id.
It is a credible email service.
It has the maximum users.
Good space available for your inbox.
Free service.
User friendly interface.
Lightening fast.
Easy drag and drop option available for attachments.
Cons: