I've always had braided hoses in the past but when building my latest bike, due to a cock-up on the ordering front, I've ended up with regular black hoses. I wanted black anyway, rather than the braided look, but I can't yet determine any noticeable performance loss from my Hope M4 Techs.

So, before I go through the faff of changing them for black braided, is it REALLY worth it on an XC bike?

No of course not.

No, and braided hoses weigh far more than stock ones.

In my experience you might feel a slight improvement on the rear brake due to the longer run of tubing, but they do seem to be much better at resisting crimping or crush damage