Matt\'s got it right... however there are actually two reasons the OGG sounds better than the MP3.
1. Like Matt said, the OGG is 499kbps vs the MP3 at 320kbps.
But also, OGG Vorbis is simply a superior form of compressed audio compared to MP3. At the same bitrate, it will sound better. Same is true for WMA (Windows), M4A/AAC (Apple), or MP4. All will give a higher resolution waveform than MP3 at the same bitrate.
Really the only reason people still use MP3s is because they want the same file extension as their old songs they downloaded from Napster used in 1998.
The reason I choose Ogg Vorbis over WMA / AAC / M4A / MP4 is simple. All those other formats are proprietary, either being designed for a specific operating system or requiring a paid license to legally encode with.
Ogg Vorbis not only happens to be the best form of compressed audio, but it\'s also free (like FLAC, and unlike WAV -- a Microsoft proprietary format).
Ogg Vorbis is also a format that will be seen well into the future. The future of embedded video on the internet is Theora video... YouTube I think is switching to this from Flash soon and everyone else is doing the same as it\'s going to be adopted into the HTML5 standards. Theora video is to OGG as MPEG video is to MP3/MP4.
Another comparison is JPEG vs PNG compressed images. JPEG is technically not free, and notorious for artifacting images (the visual equivilent of a poor compression algorithm). PNG look better, handle transparencies, and are a free format. The only reason JPEGs are still more common today is because Microsoft\'s Internet Explorer wasn\'t able to render PNGs until version 7.0.
So anyway, if you are having trouble playing OGGs, you can either choose to compromise and download the MP3s, or you can make the late switch to software that isn\'t loaded up with proprietary restrictions. iTunes being the most obvious example.
I recommend Songbird (
http://www.getsongbird.com) ... available for Linux, Windows, and Mac ... it\'s pretty much the Firefox of music players. Looks a lot like iTunes too so you won\'t even skip a beat.