Both earbuds are designed for Bluetooth devices, but the WF-C500 listing explicitly calls out broad compatibility (smartphones, laptops, tablets, TVs, smart speakers, telephones, and car audio). The WF-1000XM5 lists compatibility with Bluetooth-enabled devices and includes features like multipoint, which can make multi-device use easier when it works as intended.
If you use many different device types and want a clearly stated compatibility list, the C500 listing is more explicit; if you want higher-scoring connectivity and multipoint, the XM5 has the advantage.