Do the research and you could answer that yourself. =)
Though there's not much difference between the 2 NF7 boards, to my understanding the -S version is better becoz it has , SATA, Firewire, better on board sound?... and maybe something else.
AN7 is basicly a newer NF7 from what i read, but current issues with the board is not making a good choice for overclockers or the average consumer alike.
Seriously though dude, goto NewEgg.com or somewhere else that sells the boards, and i think you'll find they list the specs, i'm sure it can't take more then 5 minutes to read the differences.