MacDonald's is more healthier. Fried chicken will get you fat in a hurry, not to mention all those carbs in mast potatoes and gravy, plus buttered biscuit. If you like fast food chicken eat at El Pollo Loco which is more healthier because the way they do the skin on the chicken.
This depends on what you eat because a salad on McDonald´s is healthier than a hamburger, also it depends on the calorie content . This is the same case on KFC because a puree is more healthier than an ice cream. You just need to do exercise and administrate your calorie counter
Both of them are unhealthy, however, in terms of gaining weight; neither is healthier. All that matters is whether you are in a caloric surplus. If you eat in a surplus you'll gain weight. On the other hand. If you eat in a caloric deficit, you will lose weight. T