The two main things are that it is $5 cheaper at $20, and physically it is smaller. It’s only about the size of a credit card now, not that the Model A was huge either. Power consumption has decreased from 1.5 watts to 1 watt. The SD card slot is now a microSD card slot, the number of GPIO pins have increased from 26 to 40, and the RCA jack has been removed. Other than that, it is pretty much the same as the original Model A.