You lose double the information when you convert an mp3 to an ogg, and in that, you lose more quality, usually more than is acceptible.
Yeah, it says that right on the mp32ogg webpage, but I convert 100's of mp3s to oggs and I have not noticed any deterioration of quality. Perhaps just my tired ears.
On another note I just want to plug my own script because I think it is better than mp32ogg, plus it comes with a man page
You can find it at http://badcomputer.no-ip.com/linux/
just scroll down the page a bit till you see dir2ogg. It's written in shell rather than perl.