By unique you mean what exactly? =p

Last version I heard was that only Runes and Masteries armor penetration worked with skills that do not apply on-hit effect.
Actually, it's easy to test. When I have some time I shall do a test and post a feedback here =D

Sorry, that entry was specifically under the change for Last Whisper. They mean the unique "40% penetration" now works for all physical damage.

Cool! That's very nice to hear.

I will have to change my thumb rules lol.
Probally, unless I am trying to set a negative armor I will use LW instead. It saves up rune and item slots. It would fit my playstyle better :P

Id get last wisper due to cost efficiency. You generally dont want two BF items ( Assuming you take either infin or BT first) Because your trading off gold for a survive item such as phage or Qss or Guardians Which helps your team out alot more by staying in the teams longer.

under 115 arm black cleaver. over 115 arm last whisper. duno how people dont know this yet