I think I got a feel for the differences between both scenarios:

URA
>more focused runs - trainings level up with how often (You) use them
>easiest to second screen since most elements are predictable and options are visible at a glance
>external skill sources beyond supports are the random guests and g1 races
>early friendshipmaxxing and good parents hold more weight

Unity
>all rounder runs - trainings level up with your team levels
>you need to pay attention, easily adds another 20 minutes for an optimal-ish run
>easy farming runs since you're almost guaranteed 600 minimum for big 3 stats
>lots of external skill sources outside supports including ones not available yet on cards
>support hints are obscured at a glance if there are also unity balloons on the same training and possibly being overrided if they pass the roll on unity buffing
>parent uniques seem to be more easily inherited?
>landing blue balloons on the right training holds more weight than support special priority so more cards of your target stat is a better RNG mitigator than MLBs with high specialty