Trip Advisor Pro

Blogger is a free service provided by Google.It gives the option for users to use a sub domain, like mysite.blogspot.com, or to buy a custom domain such as www.mysite.com, Google Blogger also provides any time switch between sub domain blogspot to your own domain name.But once this is done there is no turning back to sub domain.
So is it worth to have your own blogger custom domain?
Advantages
1)Blogger domains have unlimited bandwidth, its better to go with blogger domain than any other hosting service.
2)Blogger domain also comes with free hosting, so you only need to pay for your domain and no need to pay for hosting.
3)Your own blogger domain can also look more professional if you are running a business.People tend to trust domain more than sub domains.
4)You will have more options with design and other features.
5)You can also sell your own domain to someone but you cannot sell a sub domain.
6)Private advertisers are more willing to pay for ads on own custom domains.

Disadvantages
1)There is no need for hobby bloggers and small time money makers to shift to own custom domain.
2)Not too much difference in features between own custom domain and blogger domain.
3)Many people are making a good deal of money without own custom domain.
4)You will have to pay for your domain, with a sub domain, you do not need to.

Hope it helped.
Also check out-
Blogger Bandwidth