XLR, RCA or BNC?

From the electric point of view there should be no difference, assuming all have clean contacts. BNC and XLR lock in place, so they won't get pulled out by mistake if you move stuff around. XLR are big and clunky, which makes them easy to handle.

I'm not sure there is a "best" termination. I like XLR for my present equipment because it sounds better than RCA. I don't know why, it just does. If RCA sounded better I'd use that.

rca bnc the same to me in digital app. rca verses xlr is a differ like on amp ,pre, and so on.xlr good for long run of wire.they are two diff monsters as in connection app.xlr locks bnc locks,wbt rca locks .you should have a talk with your friends about why they cost so much.like does a 1500.oo rca cable sound better than a 99.00 xlr cable..lol

Of course only the XLR can be used for balanced lines, and balanced XLR should not be compared with unbalanced RCA. By the way, there is no reason why XLR could not be used single ended. There are also "phone plugs" of various sizes that can be either single ended or balanced. And this is just what is common here in the USA. My CarverPro amp provides for something called a "Euro" connector.

I think XLR are best for longer cable run due to less noise due to cancelation. However, for shorter runs, say 1M or less, I think it depends on whether the "from" and "to" components contain fully balanced circuitry. Usually these are higher end, and more expensive since it requires double the parts, due to L+, L-, R+ and R-, e.g. Krell, Levinson preamps, etc. Most components convert balanced to single ended as the first step in the input stage, so If your runs are short, it shouldn't matter.