Quote:

**ReeYAwN**:

Uh... 90% of the abilities that scale w/ AD are physical abilities, thus they are also subject to armor, and arp runes would be beneficial.

Also, arp (due to the nature of the formula used to calculate damage based on armor) is increasingly powerful the more you have. where as ad is a flat increase. My point being the lower you can get a targets armor (using a combination of arp runes, items, and possiblities) the higher you damage increases.

I don't feel like doing the math, but better players than you and I are using arp runes. No offense but at level 22 w/ some napkin math you aren't proving anything.

I'll also note that in every example the damage was higher w/ arp, with the exception of 11.62 armor which nobody has.

TLDR: arp is better

Well that was a bit rude, however upon further thinking I realized I hadn't done a sample involving a high atk damage vs low armor

So we will assume again we are using Trynd who has one of the highest base attacks in the game.

At level 18 he has 111.62. Against a Fiddlesticks who has a base of 56 armor at 18. Now we are going to assume the Trynd build is going to involve an Infinity Edge for +80 AD and a Bloodthirster for an average of 80 AD. And a Last Whisper which gives +40 AD and 40% armor pen. So total we have 311.62 damage (Estimate. Obviously you can build into a second bloodthirster and keep max stacks so it could be substantially higher but in a real game you are likely to get 3 or 4 of your items and you will need at least one PD in there)

We will also assume that Fiddlestick's isn't totally ******ed and notices a well built trynd killing everyone so he will get a Guardian Angel for some protection putting him to 119 Armor

So 311.62 damage with either 14.94 ArP (For 9 runes) or 8.55 AD.

Now with a 119 armor -40% armor pen is 71.4 - 14.94 = 56.46 armor. So your effective damage is .6391 with against 311.62 damage is going to be 199.15 damage.

Now the same calculation with AD will look like 119 - 40% armor pen is still 71.4 giving you an effective damage of .5834. Starting now with an AD of 320.17 which means that your damage will be 186.78

So the total change will be about 12.37 which is indeed a pretty valid change. However all of this said, for heroes with AD modifiers that deal magic damage, which you will find is a fairly large number, having AD will help add damage to them while Armor Pen will not.

So again TLDR: Armor Pen scales well against squishies late game if you take a lot of AD items however if you plan to use AD modified magic abilities (Like Katarina's dagger/ult or Tryndamere's Spin attack) you will probably see greater benefit from your AD runes. And if you aren't taking a large amount of AD in items, (Say under the 150 mark) You will probably notice almost no difference between ArP and AD.