Hi-
Both of my children were on lactose-free baby formula when they were infants because of digestive problems. With my daughter, we just transitioned her over to whole milk gradually. She loves milk. Unfortunately, her body still didn't, and after a while, she was vomiting every time she drank too much of regular milk. We finally put her on vanilla soy milk, and she's doing fine. After all that with my daughter, we automatically put my son on the lactose-free formula, but we tried lactose-free whole milk, and he's doing great on that. It really is trial and error. You may want to try the lactose-free whole milk first, then go to soy if it doesn't work. However, we can't always find the lactose-free whole milk, or it is available in limited quantities. Also, the lactose-free whole milk is almost always more expensive than the soy (and I buy both, consisitently.)
I would also talk to your pediatrician, and he/she may have recommendations for you.