I treat all my kids differently because they are all different. My 8.5yr old (my oldest) has mild Aspergers, so he thrives on routine and having set rules, set times, knowing what is happening when. He was also an only child for 3.5yrs so he plays the grownup part more than we'd like. He's just now starting to loosen up and just hang out with his friends instead of trying to be the boss. :) He's a big helper but I never expect him to be a parent or a caretaker of his siblings. He has his own set chores and thats what he takes care of.
My 5.5yr old (middle child) is my wild man. He's always on the go, we joke that he only hits the ground every third step because he moves so fast. He's also my lover, needs lots of affection and attention. He is independent but was also the baby for 5yrs. He's funny and entertaining. He also has his own set of chores that he takes care of. No more or less than my 8yr old.
Our almost 4yr old daughter has been home from Ukraine for 5 months. She has Cerebral Palsy so there are many things she cannot do yet. She doesn't have many chores other than clearing her dishes, keeping her room picked up and making sure her things are put away. As she gets more independent in walking, talking, and being in a family she will have more chores as well. However right now she is much like a new baby that needs nurturing. She needs to be taught how to be in a family, and she is the baby. But thats what she needs right now.
So you see, each of my kids gets treated differently depending on their own individual needs. If I coddled my 8yr old like my 5yr old he'd push away and think I was crazy. If I expected the strict structure out of my 5yr old that my 8yr old requires, he'd break down. Since each kid is different, they get different. :)