One major difference after a day of listening I can say definitely, is that the ES100 does battery management much better. The Fiio BTR3 lasts about 6 hours. Please remember, I'm using 10 ohm IEMs. The ES100 lasts 10+ hours driving the same IEM. The hardware volume was set very low on the BTR3, so this for me is a major ding against the BTR3. The lack of an app to control basic functionality, and the lack of an EQ are also starting to annoy me.