Use FLAC for most music archives. It is lossless, smaller than WAV, supports metadata, and gives you the flexibility to create MP3, AAC, or other copies later.
Archiving should preserve your best source. Delivery copies can always be made later, but lost audio data cannot be recovered from a lossy file.
MP3 and AAC are excellent for playback, sharing, and streaming, but they permanently discard some audio information. That is fine for listening copies, not ideal for a master archive.
The best workflow is simple: keep one lossless archive, then create smaller lossy versions when needed.
A good archive is not just audio quality. It should also preserve artist names, album titles, track numbers, cover art, dates, and other metadata. This is one reason FLAC and ALAC are usually more convenient than WAV for personal libraries.