Udio is Suno's closest competitor. Vocal quality is comparable; the sonic palette skews slightly cleaner / less compressed, which suits some genres (jazz, folk, acoustic) better.
Udio's extend feature - adding a verse or bridge to an existing track - is the strongest in the category.
Licensing is similar to Suno; pricing slightly lower.
Verdict: pick Udio for cleaner production aesthetics, Suno for radio-ready loudness. 8.5/10.