Keep a lossless master, make portable copies
A portable lossy copy is much more useful when it is treated as a derivative that can always be regenerated.
The two-copy model
Keep one source-preserving version of the music and make smaller access copies from it. This separates archival concerns from the limitations of phones, cars, portable players and storage budgets.
Master choices
FLAC is a common choice for file-based music because it is lossless, compact and metadata-friendly. WAV/CUE can be attractive for disc-image workflows. The important point is that the master should not throw away source information.
Portable choices
MP3 remains exceptionally compatible. AAC is also widely supported and efficient. Opus is attractive when the target ecosystem supports it well. The optimal access format depends more on the playback devices than on the archive format.
Why LAME MP3 still works
LAME remains a mature way to create MP3 access copies. Standard VBR, ABR and constrained-VBR branch approaches all operate at the derivative stage; they do not need to dictate how the original music is archived. That separation is useful when experimenting with encoder settings or custom branches.
The advantage of regeneration
If a future phone supports a better codec, or you decide on different MP3 settings, the lossless master can produce a new access library. Re-encoding an old lossy copy would instead compound loss.