We only convert to XLR for long distances, that is over 3 meters up to 12 meters (then we use a 20m BNC cable. The same dirty cable that was used by Boiler Room Berlin, by the way).
We had a show last night where 2 CRT TVs were connected with adapter cables like these:
XLR cables are supposedly better at shielding the signal from interferences than composite cables (and most of our composite cables are very low-quality). We often play in spaces filled with electric devices of all kinds so we think about that. On the other hand, any kind of adapter may introduce issues on its own, and adapters quality will vary, so that’s another potential issue. BNC cables would be better on long distances but they are expensive (and BNC-RCA adapters are often shitty…see here or here). When you are on a low budget it’s a bit of the lesser of the evils.
(I was re-reading this thread and I noticed I never replied this, sorry)