As seen on the Manufacturer's website - MODEL B is the original Raspberry Pi, MODEL B+ is the higher-spec variant of the Raspberry Pi. It replaced the original Model B in July 2014. Compared to the Model B it has: More GPIO. The GPIO header has grown to 40 pins, while retaining the same pinout for the first 26 pins as the Model B. More USB. We now have 4 USB 2.0 ports, compared to 2 on the Model B, and better hot plug and over-current behavior. Micro SD. The old friction-fit SD card socket has been replaced with a much nicer push-push micro SD version. Lower power consumption. By replacing linear regulators with switching ones we’ve reduced power consumption by between 0.5W and 1W. Better audio. The audio circuit incorporates a dedicated low-noise power supply. Neater form factor. We’ve aligned the USB connectors with the board edge, moved composite video onto the 3.5mm jack, and added four squarely-placed mounting holes.