Balanced cables VS unbalanced cables for live performance use.

"But this cable is Balanced"

A "Balanced" signal is a signal that is being transmitted as 3 parts. The signal, the inverted signal, and the ground. That's why "Balanced" cables such as XLR have 3 pins. This term, however, in no way implies that the "Balanced" signal is better than the "Unbalanced" signal. The Balanced cable exists to solve the same problem the shielded cable also solves. The problem is RF interference - and the solution to RF interference is intrinsic RF noise rejection.

 
With a shielded cable, any RF noise present in the environment that might be induced into the cable will hit the ground shield first because the ground shield physically goes all of the way around the outside of the cable. Any signal that is RF induced into the cable will likely follow the shortest path to ground. The shortest path to ground, is the shield. That means a properly made shielded cable is effectively impervious to RF interference. In short, RF is nearly completely blocked by metal, especially if that metal is connected to ground. This is why Faraday cages work. It's also how they stop noise from getting into your cable line at your house which uses almost the exact same wire as an instrument cable - and much longer lengths.  

Balanced cables are also shielded, but they add a third signal - which is the inverse of the original signal. This inverted signal can be 'diffed' with the original signal at the receiving end which, in theory, could allow you to filter out any noise by inverting that noise and adding it back into the signal chain (basically the same idea that noise cancelling headphones use). This works because the same noise should be present on both the original signal, and the inverted signal. If you 'diff' those signals, the output will be the noise. Therefore, you can simply invert the noise signal, add it back into the original signal, and the output will be the original signal without the noise. However, some equipment simply ignores the inverted signal and does nothing to filter out this noise beyond the RF rejection already present in the shielded cabling - meaning the "Balanced" cable is acting exactly the same as the "Unbalanced" cable. This also assumes that the RF noise that made it into the cable only made it into the "Balanced" part of the cable, and not after the filtering. If it was induced after filtering, then there's no way to 'diff' it out. 

In many cases people are using "Direct Boxes" to convert their Unbalanced signals into balanced ones. In most cases, Direct Boxes are just center tapped transformers, which because of their construction can create the 2nd inverted signal allowing a longer cable run and the ability to "diff" the output and remove any noise that might make its way into the long cable run. However, it won't do anything to remove any noise that got into the line prior to the Direct Box, and it does add some loading to the signal possibly degrading it from the source. 

The biggest reason you'd want to use a direct box is because you're doing a long cable run in a noisy environment, and you're sure that the piece of equipment you're plugging into actually uses the diffed signal to remove any additional RF noise. However, if you're connecting your 20 foot guitar cable to a direct box just to go from "unbalanced" to "balanced", you're probably just introducing more places where RF will leak into your system, and you'd be better off plugging that guitar cable straight into your board.