My impression is perlite and/or vermiculite are primarily for drainage. Perlite retains little moisture, it just drains. Vermiculite also retains moisture. Both come from volcanic rock heated to a high temperature.
There is also plain volcanic rock, which also has a lot of air holes. I sometimes see this as a substitute, but not very often. Mixes generally use one of the first two.
Everybody’s situation will be different as to which of these is preferred. The properties look similar enough that they are largely substitutes, but costs vary by area. In my case:
Perlite is reasonable, about $9/cf. Easy to find at my local Home Depot.
Vermiculite is expensive and inconvenient. About $25/cf, but in addition, I can’t find it locally. The Home Depot about 90 miles away regularly has it so if it gives a significant advantage I can get it, but I’d rather avoid it.
Volcanic Rock in the garden stores is mostly decorative with a very consistent size and color. It’s much more expensive. There are also bags of black cinders, more or less the same thing, but again expensive because they are filtered for size and color.
I live on Hawaii Island. There are both dormant and active volcanoes here, and the entire island is basically volcanic rock. What if I just went out with a bucket and shovel and scooped up some? I don’t see why I need consistent size and color for a mix ingredient. Would a mixture of peat moss, coco coir and volcanic rock (plus amendments), work as well as peat moss, coco coir and the other two? When I buy packaged ingredients I think they are sterilized and native volcanic rock would not be, but I doubt that matters much.