...
DFI boards can get higher fsb's most of the time, assuming your proc can handle it. DFI's can get 250 fsb stock, while most new nf7-s's seem to need pin mod, vdd, and vbt do to that kind of high fsb.
I don't think you would get a much higher max oc, but higher fsb oc, meaning if 230 fsb is your limit on an nf7-s with the 11 multi, and it is the limit with the 9 multi, and the 11.5 won't boot any faster than 220 your max limit could be somewhere around 2530, but with the DFI board you might be able to do 10*250. These are all just random numbers I made up, and might be inconsistent with oc'ing results you have seen, but you get the idea.
I have heard people say that the nf7-s r2 actually performs a little better than the dfi boards clock for clock, but I haven't seen any h2h myself. With the dfi board's cpc (which you can get on the nf7's with ticta's modded bios), the additional memory timing options, higher stock fsb speeds, and vdim using 5v rail versus the 3.3v rail on the nf7-s many people perfer the dfi boards, but if you are already getting 230 fsb on an nf7 you have already purchased you should just stick with it. I bought my nf7-s r2 before the new dfi boards were out, so I am doing vdd, vbt, vdim, pin mod, nb/sb/mosfet cooling mods, which seem to give the nf7's a big boost in max fsb and overall oc, and in some cases push it past many dfi's.
Also, the dfi boards are a good bit more expensive aren't they? If I was just gettign a socket A cpu I wouldn't spend the extra.