First of all, why did you modify the post you quoted without pointing it out?

That is a good point though. I run full armor penetration marks so I never really considered if flat AD or scaling AD is better. HOWEVER, most people consider that AD marks are better for early game, while ArPen marks are better for late game, so its reasonable to assume they would use flat if they were going to use any AD.

Still, at lvl 18 its pretty easy to have over 200 AD, so the scaling AD marks still only give you an 11% damage increase, at most. Again, you have to decide for yourself based on your champion and play style.

Thanks for all the info I have changed my rune page back to ARP reds and it will probably stay that way. The only reason I was thinking of the change was for the snowball effect. Where if I was ahead with kills and caps early I could use it to my advantage later but that plan does not always come to fruition due to random teammates.

Depends on the champion and build. Scaling AD marks + Weapon Expertise + Last Whisper will give more lategame punch than armour pen. AD casters and any bruiser who likes to get a fast brutalizer are better off with armour pen as the combined flat armour pen will do Tons of Damage early-mid game. The problem with AD marks is that you're basically forced into a Last Whisper though, so I always run armour pen.

I like my AS, especially on Volibear. It's great for on-hit spells. Though I'll go ArPen on anyone that has AD scaling abilities (well, assuming they actually do physical... lol Warwick).

I usually use armor pen reds and move speed quints on melee champs and armor pen reds and attack speed quints on champs like vayne and twitch. Wonder if straight armor pen might be better on both?