I am not too surprised that you don’t hear a difference, for short runs balanced is not to important. That said, I would lean towards balanced, and the extra db is a good thing.
I have used Blue Jeans Cables and they are well made and a good value, but with gear of this quality you will hear a significant improvement by spending a bit on interconnects. I am a fan of Acoustic Zen Matrix IC’s and I have a friend with similar Luxman gear that uses them for his system.