I think b/c m4a files lack the id info that mp3's have it's a bit scary for some people to downld them. Also in my experience, m4a files are too often encoded at lower bit rates such as 128 kbps. I don't know why people are so miserly when it comes to encoding files. 320 is the best possible & so it should be done whether that be vbr or cbr. See http://www.gnutellaforums.com/showth...threadid=31710 & also http://www.m4a.com/ (this is an older site!)

One problem is the default of many apps is to encode at 128.

But yes, for the same bit rate, m4a or mpeg4 audio is smaller in size.

Actually I take that back! m4a files CAN be given id tags but 'so few' people do it! And without them people often don't know what they really are. Too few details can be deprimental to appeal. That's speaking from my own experience & from what comments I've read elsewhere about m4a files.