I bought a decahedron recently for my horse but I haven't been able to leave it in her stable for long because she is so destructive with it - she wont kick it about she'll just try chew through it.
Never had a rock and roll ball so no views on that.
love the rock n roll ball they dont stand on it and its great for chopped carrots, swede, apples etc its strong in the stable and outside on the tarmac
but not very good for feed as it falls out too fast