exe for subsequent play-thoughs, as it properly unlocks some bonus items that you normally get for completing the game.' However, it recommended that you use the newer. You'll then be able to play the game without the extra unlocks.
exe, and copy it to the Dead Space 2 folder. Simply make a backup copy of the currently installed. To remove this DLC, either play the game on Origin, or download the original. It's recommended for full effect that on the first run through you play without this DLC.
The Steam version of Dead Space 2 includes a piece of DLC that unlocks better armor and all the weapons at the start, thereby negating the need to find schematics and decreasing the difficulty.