Rundown Differences

[CrushinFelt]

What are the fundamental differences between different types of rundown hands?

For instance, the strength of

JT98 (full run)
4568 (top gap)
4678 (bottom gap)
4578 (middle gap)

That last hand is one of the main reasons I ask. It sure looks like a good rundown when someone has raised in front of me, but I have a feeling it is a lot less powerful than the other rundowns. Also, is there an inherent difference between the top gap and bottom gap hands.

And I don't give a [censored] if they're not called those things.