creating mp3 from aup vs from aiff

Greetings! Which is a better format to use as a source file: aup or the AIFF I made from that aup? I need to convert my old lectures (voice recordings) to mp3. I am an experienced use

__I notice that some of my aup files are missing blocks from the data files. But once last week, I overcame that problem by starting instead with the AIFF, instead of aup. Somehow this worked, even though the AIFF came from the aup.

__AIFF files are MUCH larger, but they were created from aup. Could the AIFF’s contain more of the original data of my voice recordings?

Now using Mac OS 10.12.6 and the new Audacity 2.3.0
Originally recorded in 2005-2007 using Audacity 1.2 ? and maybe Mac OS 7 ?

__AIFF files are MUCH larger

A good first step is stop calling it an AUP. An AUP is a tiny text file that Audacity uses to assemble all the little parts and fragments in a similarly-named _DATA folder into your show. This is an Audacity Project.

And yes, between those two, the size of the show should be much larger. AIFFs are the same sound quality as WAV files that we recommend for perfect quality backups. Nobody will be able to hear the difference between AIFF, WAV and a Project. Projects also keep editing and production information, not just sound, which makes them bigger yet.

If you have AIFFs of your work, it is recommended that you retain them forever as backups. MP3s are an end-product only (personal music player) and can’t be edited or turned into anything else without sound damage. You should read that again. The MP3 tiny file sizes are not “free.” MP3 throws away some sound quality to get there. Their talent is hiding the damage really well…once.

Further, it is recommended you keep valuable work in two separate places, not one hard drive, for example. I recently had an external hard drive take a dive and had to duplicate the sister work onto a new drive to get back to two.

Audacity Projects are not recommended for archive. It’s possible to get exactly the problem you have, bits and bobs missing or damaged. If you got clear-sounding AIFFs of your work, duplicate them and hang onto them with white knuckles.