I use MP3 mostly because they take up less space. Most people can't tell the difference anyway (quality wise)
I do recommend to use a program like
audacity to crop the files to around 25-30 seconds (or 3-5 seconds for text/email alerts)
Much (but not all) of the software available for the Q1 will also work for the Q9c. Generally a good search will yield the answer for you.
