WotLK icc10 skull vs Banner toc5n

[leeda]

may anyone check my character in armory (Leeda - Icecrown) my gs is 5,7k and the situation is the following. my armor penetration is 1215-ish when i wear the skull. it gets more when i wear the banner 1306ish. the question is the following. Which one is better at this point? i have tried to compare and simply i believe that with skull i make more DPS since its buff lasts longer and have bit more crit damage. however i know i need to get as close as i can to the Hard cap or Armor Penetration. may anyone guide me throughout this?

[invincibleh]

whispering fanged skull