It depends on your amp and how it was designed. If the amp is a true balanced design and more effort (money) put into these inputs, then use the adaptor. I have a Marsh a400s amp which even has difference specs for the XLR inputs. No doubt using the XLR inputs with an adaptor is a huge improvement on this particular amp. Experiment with using both the RCA and XLR inputs to find out for yourself.
Nothing like first hand experience and knowledge.
Bill
Nothing like first hand experience and knowledge.
Bill