There are a LOT of reasons to stay very far away from soy- especially for a young child. The more I look at it, the more I find about it. My husband is a chiropractor who studies a LOT about such things, as we have 3 under the age of 3..
You are also a lot more likely to have problems with allergies if you use soy..
Goats milk all the way- also fresh raw cows or goats milk would be best- even if you think he is allergic to cows milk, you will probably find that fresh raw cows milk doesnt bother him. (If you live near a farm where you can safely buy this- look into it, there is probably one ner you or a co-op you can go in on.)
Rice milk won't give enough nutrition if your baby is under 1.
If your child is OVER a year old, you do not have to give him milk of ANY kind. All the nutrients he gets from milk, he can get from healthy food- and get it better from the food than he would the milk. My 2 yr old twins do not get any milk other than what goes into mashed potatoes or cereal, etc. When they weaned from breast milk, they just started drinking plenty of water and eating whole foods- veggies, etc. The good fats can be gotten from avocados, fish, etc too. There is way more calcium in a small serving of broccoli than a cup of milk.