How do I to change food brands?

Abby (6 yr old, neurtered male, indoor only, not real active, very finicky picky eater) has been fed Meow Mix Indoor and Hairball control dry food (mixed together) and Friskies Ocean Whitefish &Tuna can food every since he was a baby. (I know, I know...don't yell at me). I am trying to change foods for him. I want to go to Natural Balance Ultra Premium dry and Natural Choice Indoor can food. They were rated good on their ingredients.
Here's the deal I don't understand, and after reading several post, I am still confused.
Carbs are bad...Natural Balance has 4 carbs listed in the first 8 ingredients, Meow Mix has 3.
Fat not good (for him)...Natural Balance has 18% fat, Meow Mix has 11%.
Fiber (correct me, if wrong) good (for passing hairballs?) Natural Balance has 3% and Meow Mix has 9%.

Natural Balance- Meow Mix

Chicken meal- Chicken by-product
chicken- corn meal
brown rice- yellow corn
duck meal- rice
barley- powdered cellulose
oatmeal- beef tallow
chicken fat- turkey by-product
potatoes- salmon meal

I was thinking about mixing these two together. Any suggestions?

If I decide to go strickly with the Natural Balance, and wean him off the Meow Mix gradually, what if he does not like the Natural Balance? Will he eventually start to eat it after finding out that this is all he is going to get and will eat it or starve?

Is he being finicky and picky because I am letting HIM choose what he will eat instead of ME choosing what is best for him? (sorta like your children, don't like veggies, but will learn to eat them. No, we are not having McDonalds for supper...we are having chicken, vegetables and milk)

I know that several people feed there cats different premium brands or like one brand better than the other and I am still researching premium foods.

Sorry for the long post, but I want to do what is best for Abby and trust the opinions on this site.

Thank You

Natural Balance dry is actually a very palatable cat food. I've fed the sample bags as treats and my cats never turned it down. Dry food is easier to switch on cats than canned food, all you have to do is switch gradually and slowly over a one to two week period, gradually increasing the new and decreasing the old until you are feeding 100% new diet.

But here is my concern. Natural Balance is best fed to very active adult cats and kittens. It is high in calories. You said your cat is indoors and not very active. So depending on your cat's metabolism feline obesity could be in your cat's future unless he can handle small portions of Natural Balance fed twice a day without gaining weight. And the weight control Natural Balance is low in protein and high in carbs. I like the regular Natural Balance for active adult cats and kittens.

I would reccommend something more like California Natural for your cat. It's much more moderate in calories (like 395 calories per cup compared with almost 600 on Natural Balance) and balance it with wet food (Natural Balance wet food is a good choice if your cat will eat it) because when I was feeding this food a while back my cats gained weight. In fact all dry foods are making my cats fat due to excess carbohydrates and an indoor lifestyle so I'm switching to a diet of wet food with grain free dry for supplementing wet. I'm going with Instinct from Nature's variety because it is lower in calories than EVO.