Important parameters LTP transistor matching

Hi guys.
When matching Long Tail pairs for an amplifier (BJT), which parameters do you match for? Obviously Vbe is important, but what about gain?
When designers use current mirrors to match the current through each transistor isn't Vbe the only parameter to consider?
I'm asking this as a noob. I usually match at Ic of 2,5mA.
Thanks in advance.
I explained in a post yesterday how to check the currents and voltages around the input LTP and why these voltages result in output offset.
D.Self shows a similar calculation in his power amplifier book. He also shows how close the device currents need to be to minimise distortion in the LTP.

When you do this, you begin to see why the output offset and current balance becomes dependant on the LTP device parameter matching.
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