I'm going to say, don't drink cow's milk. Too many animals die for that and it is bad for the environment. Soy isn't bad for you but if you are worried, try the alternatives.
And look, backed up by links! :p
Not bad for you:
*there's no real difference in people who eat soy and those who don't
"Thus, studies in women have mostly been consistent with beneficial effects, although the magnitude of the effects is quite small and of uncertain significance. Only three intervention studies reported hormonal effects of soy isoflavones in men. These recent studies in men consuming soyfoods or supplements containing 40–70 mg/d of soy isoflavones showed few effects on plasma hormones or semen quality. These data do not support concerns about effects on reproductive hormones and semen quality."
http://jn.nutrition.org/content/132/3/570S.abstract
"A recent study of a cohort of 952 adults who had been fed either soy formula or cow-milk formula as infants found no significant differences between the groups, either males or females, with regard to height, weight, BMI, indices of pubertal maturation and numerous other reproductive outcomes, including infertility, and cancer."
http://www.jacn.org/cgi/content/full/20/suppl_5/354S
Not bad for the environment:
*more soy is used to feed animals that are then used by humans than by humans alone.
"Still, according to a 2003 report by the Swiss organization World Wide Fund for Nature, only thirteen per cent of soybean production is actually used directly for food. The two main destinations of industrial soy production are livestock feed and agrofuels, neither of which effectively tackles food-security issues in source countries."
http://www.britannica.com/bps/additionalcontent/18/33980688/BIG-SOY
"But the UN figure is itself worth analysing. It says that more than a third of the 18% represents carbon dioxide emissions caused by deforestation in the Amazon. Nearly three-quarters of this deforestation, it claims, is caused by extensive beef farming, and the rest comes from soya growing for animal feed."
http://www.guardian.co.uk/environment/2008/jan/30/climatechange.carbonemissions