I am leaning more towards this, and have been of this opinion for the last few books. There is a metaphysical aspect to saidin and saidar which get ignored when we are trying to quantify strength levels. We are told strength is related to your soul, yet we never considered that your soul's relative importance to the Pattern might determine your strength. After all, how would you rank this? When Rand channeled hundreds of weaves in "Towers of Midnight", was this because he is the Dragon Reborn or because he has realized something about the One Power on an intuitive level that no one else has?

Perhaps women are generally "weaker" because they are so used to being in a female body that is 'weaker' physically than most male bodies, that this affects the expressions of their soul. If the One Power is a form of energy that allows for reality alteration, then your belief might express how much of the Power your soul can filter through your body before physical destruction.

Perhaps Ishamael is a match for Lews Therin because he believes so strongly that he was destined to be a match, that his soul can handle more Power than he was initially thought to be capable of, even without the True Power. It could also explain why Lanfear can be claimed to be second only to Ishamael according to the legends; when we get her POV, she focuses on being the strongest woman in the world that she might be holding herself back from being the strongest channeler in the world. She was driven both by egotism and an inferiority complex to drill the bore and date Lews Therin. Moghedien's inferiority complex and preference to work from the Shadows may drive her lesser channeling power, but when push came to shove, she used the Power to do something in T'A'R that no one thought possible - if it came down to her physical survival with her back against the wall, no holds barred, she may be capable of matching a "stronger" Forsaken because that's how her mind/soul works.

Just conjecture at this point, but it would account for Plot armor and etc.