How many people prefer to buy CDs than buy from iTunes?
If I want the entire CD, I buy the physical disk. My need for instant gratification isn't so large that I can't wait for a CD to be delivered or I can get to a store. If I only want a track or two, then I'm much more inclined to purchase from a download store, though it depends on how badly I want the track. If I plan to play it a lot, I may still buy the CD, particularly if I can find it used.
However some people say the quality of iTunes is inferior to CD, as in if you burn an iTunes song to CD it will sound inferior to the quality of an official CD. Is this true?
Yes. Tracks on iTunes, and most other download services, are compressed, resulting in a loss of quality as compared with the original source. The quality cannot be restored when you burn the track out to CD; that quality, once removed, is gone forever. Whether you can hear the difference will depend on your playback system and your ears. iTunes Plus tracks, if available for a given track/album, have less compression and so have a higher quality, closer to original CD quality, but with a high-quality playback system I can still hear the difference when compared with the original CD.
For best quality, stick with CDs and import them yourself, either at a high bit rate or for best quality as Apple Lossless or AIFF, either of which will be identical to the CD (though the file size will be much larger than with a track compressed with AAC, the iTunes default, or MP3). If and when the record companies get their heads out and allow download stores to offer CD-quality downloads with the ability to burn a CD (MusicGiants, the only company that I know of that offers CD-quality downloads, is not allowed to enable burning to audio CD), then I'll probably buy all my content from the download stores.
Regards.