Another feature I've loved in the Dead Space games is how Isaac is just an engineer. He's not some military project or even a solider; just some dude that was in the wrong place at the wrong time and learned to adapt to with the skills he knows. Luckily for him, the engineering cutters are ideal for dismembering Necromorphs.
Whether Isaac is using his kinesis module or breathing oxygen while in space, his suit has always had what was necessary to survive Necromorph outbreaks -- not to mention how it's also worked as armor vs. the claws and bites of Necromorphs. Check out the video below for all the atmospheric Dead Space goodies.