The question is too reductionist... for me, anyway. I have too much awareness of how "situated" I am, of how my loyalties are a complex (and changing) web of identities which are a providential product of time and space under divine government and persuasion. Is the *kind* of importance of the question in today's environment the same kind of importance the question had in a 4-5th century environment? How would the person I am now, in my own environment, possessing basically the same knowledge and attitudes--how would that person respond if dropped into an alien condition from the past?
We live in the fractured world of western Christendom. It is a situation we were born into, and we've adjusted. The Donatist controversy was one of the earliest intra-orthodox major church crises. These were disputants who essentially agreed about theology in the core; so a related question is: how central is the doctrine of an undivided church? In that era, the Donatist schism was a terrific scandal, creating two "denominations" of orthodox Christians. Other sects were viewed as non-Christians, for denying various creedal tenets (or at least their sanctioned expression).
I think (today) it was unconscionable for Augustin to approve and promote moving against the Donatists with force. I think it is fundamentally at odds with his wise observation that the State is a gang-of-criminals, writ large. I comprehend something of his mind, as to how he arrived at so contradictory a solution to the schism. He chose what looked to him like the lesser of two evils. Meanwhile, I sympathize after a fashion with the "staunch" Donatists, who were (in some sense) trying to call the one church to maintain its older, less-compromising policies. Was it worth "splitting" the church? I wasn't alive then...
Would I have been a Patriot or a Tory in 1776? Would I have joined the OPC or a mainline Presbyterian church in 1938? Would I have held my nose and voted for... ?
Long ago, I would have proudly announced my anachronistic allegiance to the freedom-fighters of the War of Independence, and to the doctrinal stalwarts (and "schismatics") of the OPC. Now, I am far more cautious, and self-doubting about my innate ability to "make the choice I would be proud of."