I find that things I attribute to one function could also be attributed to the other, and often I have difficulty separating the two of them entirely. To me each one seems like an extension of the other. I try to think of it like "A Ni + Fe type would probably do this, and a Si + Te type probably wouldn't, so this is more of a Ni thing than a Te thing" (and vice versa), but this doesn't always work out well for obvious reasons.
How do you distinguish where one ends and the other begins?