Isn't that such a special age???
Magic 1-2-3 isn't really all that hard.
My kids did that at this age (still try), what I learned from Magic 1-2-3 and that by engaging in the word battles with them you were giving them the power.
So if the argument is about clothes, I say "you may wear this or this, we are leaving in "X" minutes", and then I leave the room. If she is not ready at the alotted time, pick up her clothes, put them in the backpack and take her to school in what she is wearing.
We live in a fairly affluent neighborhood, and my kids see alot of excess. Whenever it comes up about how many things little Johnny or little Debbie has, I just simply say "We do not choose to spend our money that way. Money has nothing to do with how much someone loves someone" If they keep going back to the "well, she is loved" more routine, I usually say "I am sorry you feel that way", and nothing else. I don't try to justify to my kids our spending decisions.
I think the hardest thing when you get into a word battle with your kids is to STOP, don't do it...state what you want and then BE QUIET. I have finally learned to just walk away. They try to come after you with the "but, but, but", BUT if you aren't talking back to them, they don't get real far.
Good luck. Sounds like you are on the right track!
just keep on swimming!