Ubuntu 12.10 (Quantal Quetzal)
Personally I'd install 12.10(And I am running), seeing it's been out longer, and most bugs have been ruled out. I'll install 13.04, but not immediately after release.
- The bugs and error-reports in 12.10 is falling, and it will continue to fall, beginning to be a more stable release.
- Most likely a higher poweruse than 13.04 (as it's rumoured to be)
- If you're planning to run 12.10 for multiple years, 12.10 will go EOL(End-of-Life) before 13.04 (See EOL on www.ubuntu.com)
Ubuntu 13.04 (Raring Ringtail)
13.04 is the newest and feature-filled release. There is pros and cons for 13.04.
- Newer (kernel, release, everything)
- Longer support time than 12.10 once it's released.
- It is rumoured to be more battery-friendly for laptops.
- By releasetime, there will (most likely) be more bugs.
- As of right now, there's around double the amount of error-reports for 13.04 than 12.10.
- 13.04 is still in beta-stage.
- 13.04 won't be support on askubuntu.com until it's released (see the FAQ).
In the overall review, what I suggest is:
Install 12.10 now. And then upgrade to 13.04 when it's been released, and the amount of known bugs, and alike has fallen.
There is a live tracker of error reports for 12.04, 12.10 and 13.04 is listed here:
https://errors.ubuntu.com/ and I'd suggest you keep watching this after release. The amount of reports for 13.04 will fall (Although 12.10 will most likely too).