The picture is especially revealing because it assumes into existence the boxes (who brought them there?) and that there are sufficient boxes for all parties to reach the desired outcome. These assumptions map pretty closely onto assumptions about the nature of wealth that are common among more naive pro-redistribution perspectives.
What would the proper approach from an equity standpoint be if there were fewer than 3 boxes? Or if the fence was higher? What if the fence is higher and the big guy brought most of the boxes himself?
Think about fence height + 1, and 3 boxes: equality would yield 1 person seeing over; equity would yield 0 (!!!); and utilitarianism would yield 2, with the implicit conclusion that uplifting the most needy is not worth the higher expenditure under a certain degree of scarcity. Not a ringing endorsement of equity.
The comic only works because it is set up for an easy solution, and thus sidesteps every difficult moral question you could pose using that situation as metaphor.