What are the major differences between Ubuntu 12.04 and 13.04 ? That is the major reason to upgrade from 12.04 to 13.04. Is it related only to software or also hardware?
If you go to install 13.04 or stay with 12.04 LTS? you may get your answer.
I started with 12.04 but upgraded to 13.04 without noticing when I was just starting out!
Well, the Ubuntu 13.04 Release Notes page can answer your questions about what's new (see New Features in 13.04) and bugs (see Known Issues).
Generally speaking, you have little reason to stick with an older release, unless either:
If you ask me, I've upgraded to 13.04 for a while and I have yet to encounter any such bugs, and some of the problems I had with 12.10 have disappeared. (Though to be honest, I performed a fresh install because I wanted to switch to the 64 bit version, and I installed Kubuntu, not the Unity flavor Ubuntu.)