BNC vs. RCA digital connectors

I need some help with cable selection. I own an assemblage DAC 2.6 and recently purchased the D2D-1 upsampling/jitter reduction unit. Since my system is not balanced, I must use the S/PDIF connections. Assemblage provides BNC jacks and a BNC/RCA adapter so RCA digital cables can be used. I was hoping someone could explain whether there is any benefit to using BNC connectors, and if so, what I should look for in a BNC cable. I believe TPC may sell them but I would not know how to judge quality, or if there are significant differences between cables. Are there any other sources? If BNC is better, how come nobody else uses it? On the other hand, should I just use the adaptors and go with something like Canare Digiflex Gold I or II? I appreciate your response.