The first one is the BTL grounding, also known as balanced grouding. Benefited from this technology, the voltage swing is increased from 4.2V to 8.4V max; and the output power is increased to 175mW max. Moreover, the T5 has opamp+buffer on each channel, the current output is up to 500mA per channel.
The Second one is the digital volume control. The advantage of the digital volume control is it doesn't have channel imbalance issue on low volume. Nowadays, high senstivity IEMs are popular, as a result, digital volume control is very useful.
If you are seeking more advantage of the T5, the full metal case can be counted as the third one. The T5 has stainless steel top and bottom, and a zinc alloy mid frame. It feels very good when you have it in hand, is totally different to the cheap plastic case.
In addition, the whole T5 has 8pcs OPAMPs, and totally 12pcs ICs. It is a difficult task to have 12pcs ICs inside this little case. However, the sound doesnt compromise. We put many audio capacitors inside it, and it sounds truly "BIG"