Simplified: http://i.imgur.com/WKwAv.png
Detailed: http://i.imgur.com/aEpIX.png
The horizontal axis represents base AD + items (so excluding runes and masteries)
The vertical axis represents total armor

The color coding represents that the corresponding rune page is best at the scenario, and how much damage you would deal with an auto-attack.

Upcoming Changes
If you have some other rune page combinations you want me to compare with, let me know, as long as it's not too insane and obviously ineffective. ;p

Conclusion:
Full AD Marks and Quints are superior than any other combination for the early game (level 1-6) prior to buying a 2nd item.

Please note, if you rush triple Doran's or 2x Doran's + Wriggles often, you will probably want to run AD Quints, and Armor Pen Marks as it surpasses full AD when you have greater than 70 base AD + items.

So if one was to apply these computations to bottom lane's ad carry, a full AD rune page would be more beneficial early game compared to a ArPen page?

When I say full, I mean quints and marks.

I feel kinda vindicated now. I usually do full AD Marks/Quints on my AD Champs (for the +15 AD) because I think the early game is vastly improved by flat damage as opposed to armor pen and this chart seems to agree with that save for some specific combinations of armor and AD. Nice.

Updated for 10-81 armor, and 40-100 AD

Can anyone think of a realistic situation where the full AD page would not be the most beneficial? The only one I can think of is Graves and Taric vs someone who doesn't have a bonus armor aura.

Let's talk about top lane now. Since they tend to be much more tanky, would full AD be a better option?

bump