Dark Souls is better. imo, it's also easier but not really. The encounters aren't toned down and it's mostly how the systems were changed to be more forgiving. In Demon's Souls, when you died you were stuck at 50% health, or a boost to 75% using a ring; in Dark, unless cursed, you're always have 100% HP. The health item is replenished for free, so you can freely chug them down without worrying about restocking. Things like that.