It has been my personal experience that most balanced amps that have a single ended output sound better balanced. However, it has also been my experience that great amps, single ended or balanced, are great amps.
Not all balanced amps even have single-ended out, like the Mjolnir (which is awesome) but those that have a single ended output are only using half the circuit in a circuit almost certainly optimized for balanced operation. In other words, a balanced amp's single ended output likely won't sound as good. But this does not imply that balanced is better than single ended.
I've got both balanced and single ended, and it's more an issue that each has it's own unique flavor and I pick the device based on my mood and music, not the topology of the amp.