Out of the two, the 790GX-8D seems a bit more versatile, compatible with AMD's AM3 processors with DDR2-1066 or DDR3-1333 RAM (using bypass) while also capable of supporting the AM2+ CPU with DDR2 RAM. Up until now, you had to choose between DDR2 or DDR3, but not both.
The 790GX-8D also allows overclockers to increase the frequencies at any time using an onboard control dial. Users can even erase the CMOS RAM with the touch of a Reset button or switch into power saving mode by pressing the "Green Power" button.
There's also the P45-8D Memory Lover, but this P45 motherboard with DDR2 and DDR3 memory support was already unveiled in August 2008.