So when an item is detected reaching the machine, the game looks up the set of that item to better find what item that is?
or when you set a recipe with set codes for each item it only checks each item to the preset code from the recipe nothing more, if the same accept if not stays on belt
the first would require the item to be detected (does the item id for the item already contain the set number?) then learn what branch it was either copper or iron then switch the code to the relevant recipe, more computing power than the second and result in more lag and find irrelevant information all of which would have to be searched, both taking computer power and ram. This would also need more programming and testing as all of the machines work in similar ways apart from this one, requiring its own coding depending on how the others are coded
the second is a quick comparison of two numbers and one action, for each item, it might say item code detected, check against code for recipe x ( x being the recipe already set by player) is equal to one of the set recipes accept if not leave on belt, not worrying what the numbers mean just they match, one task for each machine working the same no matter how many different items
You may be right I only have little coding experience but from what little I know the second seems less computer intensive