I saw a test somewhere on the web where they tested both slugs and the three balls of buck loads (don't recall if it was 00 or 000). The short of it was that the velocity was so compromised that neither load is worth a darn. The buck had about 5" penetration into ballistic gelatin and the slug had about 7-1/2".
For bear, I'd rather have a 9mm over a buckshot or slug loading.
That being said, you'd be better off with a stout .45 Colt loading in the Judge.