Upgrading from Ubuntu 12.04 to Ubuntu 14.04

[Pep3ts]

Hello to all the list,

Im'using Ubuntu 12.04 LTS and I want to try to upgrade my system to 
Ubuntu 14.04 LTS.

Im'thinking about two ways:
- upgrade my system normally
- format my computer and install directly Ubuntu 14.04

I've a backup of all my data and is not a problem to format, are there 
any differences between the two different ways?
Install a completely new sistem can be beneficial?
Has anyone had any problem with upgrading?

Thanks in advance for any replies.

Kind regards