Difficulty:
⭐⭐⭐⭐⭐⭐⭐⭐
Controls are not always intuitive and actions are mapped to uncommon buttons. Lots of what I call "Kojimbo BS"; chief example, confining you to a small enclosed space and spawning invisible tanky enemies, ensuring you lose rations (healing item) and ammo.

Difficulty:
⭐⭐⭐⭐⭐⭐⭐
Less "Kojimbo BS" but still there. More options for combat. Easier bosses; except Solidus, imo he has too much unpredictability (still fun though).

Difficulty:
⭐⭐⭐⭐⭐⭐
Hardly any "Kojimbo BS". Easiest bosses out of the original trilogy. Subsistence version adds 3rd Person camera which makes stealth much easier than usual fixed camera.