Except the RPi is smaller, lighter, lower power and more efficient than most mini PCs. It also has a bunch of unique addon boards, many (most?) of which don't really use GPIOs, but a standard communication interface like PCIe/USB/serial/SPI/I2C.
No mini PC can beat most things about the Pi, apart from performance and compatibility, the latter of which is fully the fault of the manufacturer.
No mini PC can beat most things about the Pi, apart from performance and compatibility, the latter of which is fully the fault of the manufacturer.