An XLR connector is an electrical connector primarily used for professional audio and video electronics, as opposed to home audio/video equipment using RCA connectors. Please note that all audio outputs will provide high-quality audio output.
While single unbalanced and dual-balanced connectors are both great options, the single unbalanced option has an individual 3-pin XLR connector carrying both the left and right audio, while the dual balanced option has two, 3-pin XLR connectors for dedicated left and right audio. The dual-balanced option, which is the more common choice for professionals is arguably better for longer cable runs of 50 to 100+ feet and typically produces higher quality audio.
Please see this URL for more on balance audio.