The short answer is: It makes no difference. The XLR vs TRS comparison is unnecessary as they are exactly the same cable with different connectors on the end. So get one that’s compatible with your studio monitors and audio interface and call it a day.
Since both of these cables have balanced connections with three pins: ground, hot, and cold (also known as “tip,” “ring,” and “sleeve”), there are no ground loops that can affect signal quality; and both cables provide protection from electromagnetic interference.
XLR cables are a lot more common for studio monitors in a professional recording studio mainly due to the preference of their connectors. Studio monitors are usually mounted and connected once, then just sit there for years to come. The type of connectors on XLR cables is optimal for this.
Though to be fair, sometimes, especially with budget models, you may not have any options. In that case, just find the cable with the connector that fits both sockets and you’re good to go.
Let’s take an example. The most popular audio interface, the Focusrite Scarlett 2i2, offers only TRS line output. This is also the case for the overwhelming majority of audio interfaces.
The most popular studio monitor spot is shared between the KRK Rokit 5s & Yamaha HS5s. Both of these studio monitors offer the flexibility of using either XLR or TRS. Meaning the best cable to buy to connect a Scarlett 2i2 to a Yamaha HS5 or KRK Rokit 5, would be an XLR (male) to TRS (male) cable.
Another popular choice for home studio monitors is the PreSonus Eris E3.5. This model, as well as a lot of other affordable monitors only offers a line input in the back for balanced audio, so you would need a basic TRS (male) to TRS (male) cable.
Avoid the other input in the back, which is the RCA cable. That would be what is called “Unbalanced” sound, which, to simplify, means it is susceptible to noise interference, and thus lower quality.
Unlike most audio interfaces, mixers can tend to come with XLR outputs. If that is the case for your mixer, then you’ll most likely need an XLR (female) to XLR (male) cable, or XLR (female) to TRS (male) cable, depending on the input available on the back of your studio monitors.
Either of these two options will work perfectly fine for your setup!
At first glance, TS cables may look identical to TRS cables. But the wiring inside is different, making it “unbalanced”, and as we mentioned above, susceptible to noise interference. This makes them not recommended for use with studio monitors. You can differentiate a TRS cable from a TS cable simply by the two rings at the tip of their connectors.
It really doesn’t make a difference, but if your studio monitor does offer both options, then go with the XLR cable. If your studio monitors only have a line input, then the TRS will work just as well. You do not need to shop for studio monitors based on their input type.
As long as you avoid TS or RCA cables you’ll be grand. As those can cause introduce unwanted noise in your signal chain due to ground loops that are created when two unbalanced lines connect together at one end.