There are not a lot of big changes in DKS compared to D2:ED (though in your case the engine improvements make a significant difference in performance), but there are many little things that add up.
It is possible someone may want the original release of D2:ED, but I'm not sure why, especially since DKS is $10 cheaper than getting D2:ED and FoV separately (and DKS occasionally goes on sale on Steam, etc; see
here). Impulse has links on the D2:ED and FoV product pages to purchase the opposite, but nothing saying they can be bought together as DKS, with updates to the D2:ED part of the game.
