Just to add to the above post in another way of thinking about it...

If I make some chest armour and parent it to the chest of the figure, the armour would sort of move like one would want but need additional tweaking/moving into place. This could be okay for a still shot but not for animations, however the armour would be solid and not bend...ie; like real armour.
If I make some chest armour and conform it to the figure then the armour would move with the figure identically and could be used for animations, however the armour will also bend as the body parts bend and move...thus resulting in maps being smeared and armour bending.

Kind of tough to explain unless you see it for yourself.
There is a time and place for both, you just have to pick and choose your pieces and how to parent/conform them and when.

Hope this helps.

Comitted to excellence through art.