Well if you have a champ like shaco or ashe that gets 100% crit chance through their passive/ability then crit damage is a lot better. Trynd with crit damage is crazy but you need around 20-30% crit chance from items so he can keep his charges up.

Well, I'm kind of a noob but, you've got crit damage and then crit chance right? If your crit chance is high, then the value of crit damage increases. So if you have a low crit chance, then crit damage is worth a lot less. I guess what you need to know is, for your champion and build, what is the breaking point where crit damage becomes less important than flat damage, point for point?

Maybe there are other factors? I'm not sure.