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I'm using Ubuntu 12.04. And can any one please tell me what difference between Ubuntu 12 and 13 and what version of Ubuntu is better. Why?
12.04LTS stands for “long-term support.” LTS releases would be supported with security updates for years.
However, Ubuntu also have new releases every six months. Every new release of Ubuntu offers new features. The current release being 13.04
LTS releases will receive security updates and other bug fixes as well as hardware support improvements. The current LTS release, Ubuntu 12.04, will be supported until April 2017.
Now, a regular release like 13.04, will only be supported for nine months. Considering new versions of Ubuntu are released every six months, you’ll have three months after a new version is released to upgrade to it or you won’t receive security patches anymore.
Well, if you want to have the latest versions of all your software, and use the latest features before they make it to the LTS version of Ubuntu, upgrade to the every-six-month releases. Now its 13.04
However, you’re not missing out much by using 12.04. It’s regularly updated with new hardware support and performance improvements.
On a personal note, I'm still using 12.04, and haven't upgraded to 13.04.
Also I would read the release notes as per gertvdijk comment above.