It doesn't matter which you use, as both TRS and XLR are balanced. If your outputs are balanced then go ahead and use balanced cable. It may be easiest to stick with the 1/4 inch TRS cable if your soundcard already uses 1/4 inch outs. Look up and check that your outs are balanced. If not, it could cause problems for the inputs in your monitors as they are designed to have a certain type of connection/signal.
XLR offers some good qualities over the TRS. In the case of microphones, the 48 volts supplied by the preamp is on two of the connectors. These connectors are separated by space at all times. In TRS, the connectors interact with other elements, so there is a quick moment when there is a short as the connector is being inserted. Sometimes you'll see an XLR patchbay for this reason among others.
Use whatever cable is best for you. If you are willing to learn, you can make the cables you need out of Mogami raw cable part number W2549
and a neutrik connector. Very cheep to make and you get very high quality.