In the following chapters the percentages tell you how much the value of resources increase by refining them in each factory.
<> 1 iron > 1 steel //1 iron is refined into 1 steel
<> 10 cred > 12 cred //1 iron is worth 10 credits before and 12 credits after refinement(in the form of steel)
<> +20% //increase of value as a percentage

The max amount of a resource that you can stack:

Iron: 5


Tritanium: 5


Carbon: 4


Copper: 5


Gold: 5


Uranium: 5


Sulfur: 5


Steel: 20


Tri Steel: 20


Diamonds: 5


Coils: 20


Hyper Coils: 20


Processor: 5


Enriched Uranium: 10


Ammo: 20


H.E Missile Parts: 10


EMP Missile Parts: 10


Nuke Missile Parts: 10


Mine Parts: 4

stack up to 20 > stack up to 4
value +25% < value +940%
copper and coils needed = iron and ammo needed
needs 2 factories = needs 2 factories
0.2 H-Coils/30cred/sec > 2 mine parts/26 cred/sec

Since Mine Parts make way more profit and are made of iron and ammo (which is made of sulfur) which are more common than copper and additionally give more than twice the profit relative to cargo space they would be the way to go. Nonetheless, Mine Parts take up way more cargo space, will fill up your storage quickly and you need more crew members to transport them to your storages which can delay the production and result in less credits per time. But the main problem is to find enough buyers to sell all your Mine Parts, which will take the most time and decrease your profit per time. At some point all stations will be saturated and you'll have a hard time getting rid of your spare drone parts.
on the other side are much more efficient in that matter. Furthermore they allow for a construction line consisting of a Coil Factory and a Hyper Coil Factory whereas you only need copper to keep it going. So this is my recommended method of making quick money through asteroid farming!