The two versions will contain different versions of the ADSL driver. 023o will be the more recent driver, which is usually but not always the better choice.
I did not see it like that so guess I am wrong.
I thought you had to match the same driver as in the current system looking in the GUI.
In my case:
ADSL Firmware Version: A2pB023o
.d20e so I was going to pick the 023o anyway.
And I thought there was three versions to pick from.