Tough one. The problem for me is that neither word is well defined.
What is justice? For whom?
What is compassion? I know what it means broadly, but compassion to dying and diseased 90 year old is different than compassion to a teenager.
This is one of those where situation / definition really is important.
Therefore, too broad to answer.
(And yes, I have been tested myself, and I had pretty much the same feeling then that I do today)