I think that this is something that you would have to try for yourself. MOST think that biwire is an improvement but not all. Some hi end speaker co. do not offer it , altho most do. There is no requirement that both sets of wire be the same. They will have different tasks and it may well be a good idea to use dissimilar wires. For years the accepted wisdom was thick wires for bass and thin for mid and high. I will not defend this as an absolute principal but it has some logic behind it. I am currently using Mapleshade and Anti cable as biwires . I have used identical Siltech silver wires in the past so I am familiar with using identical wire. Wire companies will make up custom Y plugs if that is a help.