Yes there were some 200 or so BA, now down to 150, and there may be a more even split among Asha'man, so let's say max of 500 AM for the shadow (we're up to 650 total). Maybe Mesaanna will pull out some Novices or something, but they (1500+) seem to be pretty solidly behind Egwene and her 700 or so channelers, not counting the Kin. Then Rand has like 500 AM, tons of windfinders and Damane and Wise Ones, and ALL the known angreal and sa'angreal unless Graendal managed to survive and keep hers. Plus, the Light actually uses circles and cooperates. I think, at least right now, but I am sure that someone else has done a better compilation that the Light has well over a 1000 channeler advantage in addition to all the other strengths of angreal and circles and discipline. The Ayyad are the biggest unkown, and they could definitely tip the difference. They may have been under Ishy's influence for some time, who knows?

Basically, the shadow is shown to be strongest where there are the weakest personalities and fewest checks on any kind of power (the Aes Sedai and the Asha'man). The Aiel, the Sea Folk, and the Seanchan all seem to have FAR fewer darkfriends as their senses of honor and obligation are much more deeply and broadly ingrained.

I personally think that the Forsaken are mostly a sideshow to the real power of the DO, Shadar Haran, Moridin, and the hordes of shadowspawn. So it may not matter overly much that the Light has any advantage in channelers. We'll see though.