Best method to disable Radeon card in 2011 MacBook Pro?
gfxCardStatus disables the automatic graphics switching that macOS performs when a high performance application wishes to use the discrete graphics. When macOS boots, it detects both GPUs and uses software to switch to the discrete graphics when required. Since both GPUs are detected on boot, both GPUs are powered up, though the discrete graphics quickly switch into a lower power mode until required.
Disabling the discrete graphics using the kext method completely disables the discrete GPU so it doesn't power on. This is especially useful if the GPU has an issue that causing the machine to kernel panic. The gfxCardStatus method wouldn't prevent this, but the kext changes would.