What is the difference between XLR cables and TRS cables in a live environment and in a recording environment? Which should we use in a performance? We are contemplating whether to do it inside or outside a musical festiva.
XLR cables are known to be shielded twisted pair cables for balanced connections, TRS cables can be intended for headphone and/or unbalanced stereo connections, making the cable geometry, twisting and resistance more of a gamble. Assuming that you actually use balanced connections at low signal levels over non-trivial connection distances, XLR tends to be the safer choice for not getting some unsuitable cable in between. In particular, I'd be wary using an extension cable on balanced TRS: that implies a long connection and a male/female TRS cable that is more likely than not a headphone extension cable not designed for balanced use.
For line-level connections, the sockets tend to be TRS to TRS anyway and the high levels make the impact of cable geometry comparatively small, assuming reasonably short connections.
Of course, if you solder all your cables yourself, it's up to you. The guaranteed connection process of XLR (any contact is present or not and not shorted with other contacts) is a boon for things like phantom power.
As has been said above, there is really no such thing as an "XLR" or a "TRS" cable. These are connectors. There is, however a big difference in the "type" of cable that can be used between these connectors, which may specifically apply in your situation. That is the use of "starquad" or "non-starquad" cable.
Starquad cable is a form of balanced cable which has two conductors for each signal path (+ve phase and -ve phase). These conductors are arranged at the corners of a square so that each identical conductor is opposite its pair and the opposite phase appears at the other two corners. A slight twist is introduced during manufacture. These cables are also well shielded with a ground braid connector.
This type of cable has been shown to exhibit superior coincident rejection of induced signal over standard three conductor cables so are particularly suited for use in environments where you may not have control over where the signal cable is being placed, i.e. next to lighting ballasts and other mains cable.
For a music festival such as the one you mention, you will need Neutrik XLR Connectors and lots of starquad. These days most long cable runs are done digitally but if you are still going analogue, then starquad is the way to go.