I can't really drink too much milk, so tend to have soy milk since it's quite high in protein. I can drink the sweetened stuff plain, but the unsweetened is
by itself - ok in protien shakes though!
There is so much contradictory press out there on both soy and cow's milk, I figure if you find 1) something you like the taste of and 2) doesn't have you running to the loo every 3 minutes and 3) doesn't produce any other nasty side effects in you personally then go for whatever you feel!