@DonH56 It would generally be higher noise in differential, no? distortion generally marginally better on even harmonics, but yeah unless you are dealing with long cables, not really worse or better. As you say, all about the implementation and for measurement I believe you need both (or at least its desirable). Some of the quietest amps i've ever seen and heard are single ended. That being said, at least in my case for a DAC, creating a SE output would mean a further stage and be slightly more expensive. If i'm using a balanced dac, I typically use a balanced output and a high performance FDA is about the same price as an opa1612.
For an economic reason only, my solutions are cost-effective by conception. Yeah, my notch uses simple and cheap C0G caps,(actually, Samuel Groner also recommends C0G for his passive notch), but I don't want to adjust 4 trimmers instead of two, and increase the parts count twice.why you'd need to add a stage for a SE output
I do not quite get why you'd need to add a stage for a SE output unless using one side of the differential output causes too much of a performance penalty (that is often true, requiring a single-ended to differential converter at the output).