I'm pretty sure "inconsistently principled" == "consistently unprincipled".
With the second reading, a tangential concern is what drives the inconsistency. If it is purely stochastic, then I think the above saying holds ("better to be..."). If it is manipulated by unprincipled agents, then it's much more questionable.
https://en.wikipedia.org/wiki/Equal_Protection_Clause
There's also a long history in cognitive science on social trust and perceived consistency (anti-hypocrisy).
https://en.wikipedia.org/wiki/Cognitive_dissonance
So that is why people normally vet these issues outsied of the context of SCOTUS, even on social issues. These are valid ideas irespective of people's views on any subject, IMHO.