Different scenarios will have ships that drop different material types. I prefer anarchy systems with tourist beacons (a stupid, deadly combination tbh) where I can camp out in my G5 rated vette and destroy passenger ships and have at least 9 limpets running full time. I will say that, since the most recent update, the passenger ships won't engage, they will flee. In the past you could have two at a time blow up next to you since they are stupid and try to engage with their small pew pew and risk/lose all the lives on board. Then I can go to CNBs and collect other types, or drop into convoys (funerals, military, etc... ) and kill those ships as well ( in anarchy, unless you don't care about notoriety). They will have even different materials.
Dav's Hope is cool, but I hate relogging to do anything. It just feels stupid.