The "witnesses" are talking ballcocks. Once you get to about 5M, I would say unbalanced is a no no. You may get away with it 9 times out of 10, but eventually it will bite you on the bum. @rmorris got it just about right.
Of course, you can use a TRS connector rather than an XLR for a balanced feed (I believe the HX Stomp does this). However, having an XLR output that is balanced will cover more bases. Added to that, an XLR is locking as standard, and they are easier to lengthen just by adding another cable, something jacks cannot do.