Well for me the main difference is the output impedance of the two jacks.
Single ended 3.5mm is 2 ohm.
Balanced 2.5mm is 1 ohm.
This makes a difference when using decent multi driver IEMs especially.
I can easily test the subtle differences with my Centrance Hifi-M8 which has an impedance switch of 11/2/1 ohms.