Stratix Professional Edition vs Cyclone Edition

It's due to the FPGA populated on the board. The main differences between the two boards are 1) The Stratix part (1s40) on the Pro board is much larger in terms of logic elements and memory resources compared to the Cyclone part (1c20). 2) The Cyclone board has an EPCS device (it's a storage device that you can put your hardware design and software into). Everything else is the same (SRAM, SDR SDRAM, LAN91c111, Flash, Proto headers, etc....)