Ok so I have 2 builds in my mind, but which one will perform better?
Marks - Armor Pen
All the rest - Crit damage
Giving my a total of :
Armor Pen = 14.94
Crit Damage = 25.44

OR

Quint - Armor pen
All the rest - Crit damage
Giving me a total of:
Armor Pen = 9.99
Crit Damage = 32.13

(All T3 runes)

Now this build is made for Yi, Trynda and Gangplank. I did a full crit build when I was level 21, I owned everything. But now that I am level 30 I was wondering how much armor pen I should get.

Neither of them is a better build, because crit damage is a horrible stat to rune for.

If you want to crit harder, get armor pen. You'll do more damage on your crits until late game swings round, and even then the difference won't be big.

Getting crit runes is really not that bad. I'll let you know my common games before level 30 with Yi were on average about 30/11/15 something like that. But thanks will take it into consideration.

No, getting crit damage runes is bad. Okay, sure. You might have had games where you did well with them, but you'd do even better if you used armor pen, because the crits you get will do more damage, and your non crits also do more damage.

The only time crit damage becomes useful is late game. By late game, your crit damage runes edge out armor pen a bit, but even then, does it really justify a weaker early-mid game just for slightly bigger red numbers later?

Ye I get what your saying. Suppose I will go for the Armor Pen then. Thanks.