The main difference between a USB 2.0 cable and a USB 3.0 cable is the transfer speed. USB 2.0 cables have a maximum transfer speed of 480Mbps, while USB 3.0 cables have a maximum transfer speed of 5Gbps, which is about 10 times faster. Additionally, USB 3.0 cables have additional wires for improved power delivery, have different-shaped connectors, and are backward compatible with USB 2.0 ports.