Assuming the high-vote count Idea for matching on latest version Process Builder flow between source and target (and not by version #) is implemented; make the visual comparison between source/target PB not solely XML.

Process Builder in XML can't be deciphered by a human mind. Hence, a simple indented text-based visualization could be done to make it more readable

1. Decision 1.1 Entry criteria 1.2 Immediate actions 1.2.1 action 1 details (XML here OK) 1.2.2 action 2 " " 1.3 Scheduled actions 1.3.1 scheduled action 1 (XML here OK) ...
2. Next decision ...

There's an implicit tree layout in the PB visual editor, need something to mimic that in gearset and color code diffs (red/yellow/green)

Of course, mimic'ing the graphical view in SFDC or something like it would be even better

If you want a system wherein there is a way to be sure your PB changes aren't smashing the target in an unexpected way; this is essential.

Doing the same for Visual Flow is harder is the layout is arbitrary so let's start with PB (something more prevalent in orgs than VisualFlow)