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.
The BNC connector is the industry standard, being the only true 75 ohm connector. The impedance of the interconnecting wire ( including length ) , the requirement of the termination of the involved components, and the impedance of the connector itself, all effect the end result. No easy answer in absolute terms, except to say that if the two pieces involved required a TRUE 75 ohm termination, and the cable was a true 75 ohm cable, the BNC connector would not alter the balance. If any piece in the chain is above or below the 75 ohms, the connector could be "off" in the opposite direction, and "correct" the termination. To further complicate things, the quality of the connector and cable are almost as important to sound as maintaining the 75 ohms. Like most things in high end, you should audition several good quality cables and listen to the effect on your components. The only head start could be provided by the factory, who could tell you how important the termination capacitance is for your two pieces of equipment. If they say that your pieces are designed to work, using the supplied adapter, you are set. If they say that the 75 oms needs to be maintained, and the adaptor is a compromise, you should get a run that is terminated correct from the beginning, using the BNC standard.
Thank you Albert. I will check out cables with BNC connectors, to try and stay with a true 75 ohms.
FYI, has a Cambridge Audio BNC digital cable on sale for about $35.