K.B.
I used to be like some of the moms here and wanted my son to listen to me and do as I say. But then I realized that my son really does not have much control or say so in his life and to give him choices would really make all the difference in the world to him. And it did.
He used to fight me on taking baths, eating and bedtime but also on every other thing that I would want him to do. If you think about how much a child that age can actually do by themselves there really isn't much. It must be frustrating for them to be so limited and always relying on others to do things for them and then not have a voice on some of the more trivial things like clothes and shoes.
Let him choose his clothes and if the choice is not a good one for the weather (or the type of outing) then explain that to him. I think children get frustrated when we don't tell them "Why" we ask them to do what we want them to do.
Try to give him more choice (not just with clothes but with foods, books for bedtime,toys etc..) and see where you go from there.You might just find that he isn't so combative.