There is a lot of mythology behind balanced connections. I think they are often "over sold" for most consumer purposes with short runs. They have subtle benefits regarding noise and hum but only in some
circumstances. The myths arise because people see pros use them so they assume they "sound better". They (pros) are much more likely to reap the benefits because they use markedly longer runs in studios and on stage, but a typical consumer usually uses 1M, maybe 2M runs if everything is in the same stack, and the likelihood of the wires acting as antennas and picking up additional RFI/EMI noise along the run is much lower. Sure we have noise in prepros, sources, and amps but it's predominantly thermal
noise [the noise all electrical gear has] and XLRs, if working properly, will conduct that
noise quite perfectly from point A to B.
"That noise you hear in your system is from the wires, ya know" is the goto wire company/dealer scaremongering ploy. There is a grain of truth to it so it is easy for them to rig up demos to con people.
The sound is otherwise 100% identical, XLR to RCA, in all "sound quality" regards so when you read a silly reviewer talking about "better imaging by using XLRs" that's baloney and their imagination.
If you use RCAs and find no noise or hum issues, which is usually the case, any investment in converting to gear using XLRs would be a waste. Also keep in mind there are many reasons for hum and noise so going balanced isn't a sure bet you'd be cured of that noise.
Oxidation is hard to see but will be obvious because the sound cuts out. Often simply breaking and remaking the connection will scrape the grime off and you'll be good to go for another year, or you can use contact cleaner spray like Deoxit.
The two ends of XLRs are different, by the way, and with locking only on one end, not the other: