What's the difference between balanced and unbalanced output?

Balanced outputs (4.4mm or XLR) typically deliver more power and, on some designs, lower noise, which helps with power-hungry headphones. Reviewers note that for sensitive IEMs and easy-to-drive cans the single-ended 3.5mm or 6.35mm jack is usually indistinguishable in practice, so balanced is most worth seeking out if you own demanding headphones.