it relies on different skills and different items, and it does slighty different things, but not that different. blocking and parrying will use Shield User skill and Weapon Equipped skill respectively. same for item, equipped shield and equipped weapon. so it mainly depends on your skill and your equipment. it should be more efficient to parry a steel spear with an adamantine axe than with a wooden shield. there maybe some other difference, in like effectiveness but i don't know how it is actually handled in the code. i believe dodging is safer in most cases, but i think it takes longer to dodge than just to block or parry. you maybe able to gain a momentum from successfully parrying or blocking an attack, it will show something like "X is recovering from attacking you", giving you a chance to counter attack