Very intersting question, I've thought about it a fair amount before. I think one important thing to remember is that you can have exceptional recording/mixing/and mastering in any of the formats, so it is unfair to make a blanket statement that one format is better than another based on one or a few recordings. I personally agree with Jorge, Kelly and Sugarbrie in that most recordings (esp Classical or music with a lot of timbre)I have that are AAD or ADD sound better than some of my DDD recordings. On the other hand, I have some exceptionally good DDD recordings. I personally think that analog recorded +/- mixing tracks sound more natural than DDD ones. I also think that the best vinyl sounds better than the best CDs. That's purely my opinion, and opinions are like... Anyway I think most of a CD's quality is based on the efforts put into making the music, recording equipment, number of discrete tracks, mixing ability of the folks at the company, etc. more than just the format. I would just look for CDs I really like. Hope this was helpful. Happy listening,
Todd