I don’t really think there are any audible differences between one properly designed and built (i.e. appropriate materials and gauge for the signal being carried) connector and another, regardless of brand.
To the extent that people do hear differences in such things, I would say it is almost certainly down to expectation bias.
This is not to say, however, that different connectors (or wire, or finished cables) don’t have different electrical characteristics (resistance, capacitance, internal reflections/structure)!
They certainly do.
Though you need fairly specialized (and extremely expensive) equipment and techniques to measure those differences. It’s not something you can do with a standard multimeter or audio analyzer (even the high-end ones … they’re built for a different task).
But even so, the effects of these differences in electrical characteristics don’t tend to show up at audio frequencies at all. And the mechanisms those different characteristics have to change sound, i.e. altering impedance or capacitance (which with dynamic headphones can form an LC filter in conjunction with the coil, that would affect frequency response) require much larger changes in value to be material anyway.
Now, saying one connector “is as good as another” depends how you define “good”. For audibility-purposes, yeah, there’s probably nothing in it. But there are many other practical factors when choosing connectors, even beyond their electrical characteristics … and those are generally what drives which connector or brand you choose … even if sometimes it’s just how they assemble and aesthetics.