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.
