PolyLists and their meanings?

[b]abstractPolyList[/b]
This is the abstract class other polylists are ultimately 
derived from (cannot be directly instantiated). In other
words, a base class.
[b]clippedPolyList[/b]
This clips a single poly against the polylist, creating new 
surface clipped and surface aligned polys (this is used by 
the dynamic shadow class, so shadows conform to interior 
and terrain surfaces).
[url=http://www.garagegames.com/docs/tge/engine/classConcretePolyList.php]concretePolyList[/url]
This is the basic workhorse polylist (nothing fancy, just 
stores data).
[b]earlyOutPolyList[/b]
[url=http://www.garagegames.com/mg/forums/result.thread.php?qt=4759]extrudedPolyList[/url]
This one only computes collisions in the given direction.
Very practical and effective for player type 
objects, but not for more advanced objects like vehicles.
[b]optimizedPolyList[/b]

I have threated these the same until today when I browsed trough one of the source files and realized they were alot different in some cases. The only one that makes sense to me code-wise, is abstractPolyList.

There's no documentation to be found about them, what they do or where you should use them. I know earlyOut is used (for performance reasons?) in Player as a way to quickly check if a collision has occured and then skip the rest of the calculations. But I dont know why it's faster or what it really does.

If anyone could do a quick rundown of the strenghts and cons of these I would be a happy guy! Thanks.