Which do you believe your own existence is in greater concordance with and which do you think is the superior value?

The Golden Rule being that you treat others as you would have them treat you, not how others have treated you.

The Golden Mean being all things in moderation.

In my understand of this the Golden Mean is about moderation while the Golden Rule is in contrast about generosity, at least as Jesus interpreted it, I believe this is why when he was approached by individuals with legalistic mindsets asking how giving and loving they should be he gave almost absurd examples and parables reflecting and infinite generosity.