Ok. Soy has isoflavones, which are kinda shaped like estrogens, and bind to estrogen receptors by chance cause they have similar structures, but not as strongly as real estrogen, because they're not sex hormones to begin with.

Cow milk has actual estrogen. Because cows are mammals. With actual sex hormones. Which binds strongly to estrogen receptors, because that's what they're for.

I know which one I'm going with.

Are you sure about this issue with normal milk? I cannot find much about it although the soy estrogen research is all out there.

I found a few studies by googling 'dairy estrogen'.

To be honest I don't think it's that big of a deal in either case (soy or dairy), for occasional consumption, I eat both on occasion. But if we are talking about replacing meals with a dairy shake, or GOMAD (gallon of milk per day, a 'traditional' recipe for fast weight gain), I might be a little bit concerned.