Good question!
XLR certainly does reduce SOME of the effects of cabling due to it's design. XLR is balanced which means there are 2 signal conductors, one being the inverse of the other, and at the receiving end the idea is the signal is the difference between the two signal legs. This means that any noise the cable encounters will hopefully effect both signal legs equally and thus will be canceled out at the receiving end.
However, the materials and geometry of the cable still make a difference because the geometry will change the amount of capacitance and inductance in the cable, and the audible effects of the conductor and dielectric do NOT get canceled out either. There is ONE particular person who regularly posts on some sites that claims that using XLR, if PROPERLY implemented (like this is some sort of esoteric knowledge, lol) then the cables make NO difference at all. This is a myth that I honestly think this person believes, but because this person's entire professional career is based on the claim that balanced is better, he's massively biased and it seems all this is based on a simple test performed decades ago and NOT based on a broad number of tests over many systems. I've been sending people demo cables for around 10 years now and I can say with certainty XLR cables make a similar amount of difference vs an RCA cable, because with a properly built interconnect cable, the materials dominate the way the cable sounds. For example, the thought that a copper and silver cable will sound exactly the same is seriously misguided, and reflects an inability to even entertain the thought that these beliefs should be revisited.
For home systems there are hotly debated pros and cons to balanced vs single ended, in many cases the noise-rejection of XLR, which is designed for pro-audio, isn't required for a home system that is far simpler and uses MUCH shorter cables than a live sound venue or studio. OTOH almost all modern DAC chips produce balanced output so we are forced to deal with the fact many DAC's balanced outs are better than single ended.
So for the plugs... yes the $$$ CF-600 series Furutech plugs are definitely worth it. Plugs make a big difference, and if you're going to build a cable using UPOCC silver, which costs a fortune, and it's main advantage over much cheaper silver is it has no harshness, thinness or fatiguing artifacts, and then use plugs that add grain, and fatiguing artifacts, you just really compromised the cable. Unfortunately, top-end XLR and RCA plugs are not inexpensive, and add that to $$$ super-high-purity OCC silver, and you get an expensive cable. However, due to direct sale I'm able to offer such cables for reasonable prices relative to dealer sale brands.
I'd also say many cable companies cheap out on plugs because they are very expensive. I've seen many look-alike Furutech plugs, even used on a top end, "front row" XLR cables. These look like Furutech but if you check Amazon you can get them for a fraction of the price of genuine plugs. This is VERY common. I also see a lot of RCA plugs with non-locking 100% plastic bodies. These are fragile and force a tiny ground contact area over the jack with too much force, this tiny contact area will quickly wear. Locking plugs prevent this issue and while more expensive offer the user far more useable connect/disconnect cycles.
So in summary, just like everything in audio the plugs are part of the system and it all matters.
