Se sonner isn’t actual French. Your other alternative is correct though: one would say “Ça sonne mieux” or “Ça sonne moins bien/pire”.

In the sense of word choice, the literal translation is not appropriate. Instead, you may say “X convient mieux que Y”.

If you refer to music, you may keep a literal translation, e.g. “X sonne mieux que Y” or say that “X est plus/moins mélodieux que Y” or “X est plus/moins harmonieux que Y”.

Note: Depending on the verb (verbe d’état ou verbe d’action), the
opposite of “mieux” is either “moins bien” or “pire”. With “convenir”,
use “moins bien”. With the auxiliary “être”, use “pire”, e.g. “X est
pire que Y” or “X est le pire des deux”.