I have light and full cream in the house. It's more of a taste thing for me, I like full cream in my coffee and light in my tea
The kids generally drink the full cream but sometimes they get light. Looking at the label my light milk has 0.2g/100ml more sugar than the full cream, not something I would worry about.
I would be interested in learning more about the actual difference in the processing of light vs full cream though...
In general we eat mostly whole foods in our house and not a lot of milk is consumed so i'm not too concerned about one being better than the other.