Actually, from the AOL perspective, this is true. Men and women were equally strong if you calculated strength from what they could accomplish as channelers, not from the volumes of saidar/saidin they could control as otherwise the comparisons between men and women are totally off. On average, men can control far greater quantities of saidin than women can of saidar. However, women are able to accomplish more, and more precisely, with a smaller quantity of saidar when a man needs to use a greater amount of saidin to match what she does, so ultimately things are balanced out and if you look at channelers as a whole, the genders were equally strong, one better suited to some tasks, the one to others and so on. The current Aes Sedai judge strength based on the raw quantity of saidar a woman controls, so from that perspective Moiraine was indeed wrong: men control greater quantities of the One Power and Tower-standards, are thus "stronger" on average than women. But Moiraine was going by AOL comparisons from books and such, and wrongly applying them to the Tower system to judge strength, thus her confusion.