Path of Exile has two stats that aid players in terms of gathering loot: Item Increased Item Quantity and Increased Item Rarity. Some players refer to this as Magic Find or MF but technically, Quantity and Rarity function in different ways. Here’s the difference:
Increased Item Quantity (IIQ) raised the total number of items dropped by monsters as you go through your grinding or farming run. For example, what should’ve been a drop of 2 Blessed Orbs would become 4 Blessed Orbs if you have a +100% IIQ in effect. As you can see, this raises your chances of acquiring items and building your financial capabilities quicker, although expect to see a whole lot of junk when this stat is in play. It would be recommended to have a spacious inventory if you plan to farm for items and equipment with IIQ in effect.
Increased Item Rarity (IIR) on the other hand doubles the number of Normal (White), Rare (Yellow) or Brown (Unique) items that you would find as long as it’s in effect. This is best used in areas where a certain piece of good equipment drops from a boss or whatever. This does not necessarily doubles the items that you loot but rather, gives you a better chance of avoiding junk equipment.
Most people say that IIQ is better than IIR since the number of drops that’s triggered by the skill also affects your chances of acquiring good equipment, especially if your Exile is adept in killing mobs efficiently. It is common practice for solo PVE runs to have +150% IIQ and +50% IIR. Having these 2 stats at equal levels are rarely beneficial and more often than not, the effects are not evident. It’s a good rule of thumb to either favor IIQ or IIR then have the other as support.
Getting as much IIQ and IIR is of course every Exile’s dream, but given the price tagged for pieces of equipment with these boosts, only seasoned and veterans can only afford them. With that being said, if you’re farming along with a party, then you may consider boosting IIR since a full roster has generally about +250% of IIQ factored in. But for solo runs, get more IIQ so that your Currency Items builds at a much faster rate along with your chances of obtaining good equipment.