I notice a difference between different portable DAC/amps and I have a strong preference for two devices from the same manufacturer but, I wouldn't describe the difference as like night and day, more like good and a bit better, I can enjoy the other devices that I rarely use. Maybe they get more out of their gear than I do, I wouldn't like to assume that they're deluded, if there are people who think that all headphones sound identical, there are probably people who pick up on very subtle differences between devices.