What the body does with one input versus a different input is much more important than the quantity (caloric) of each input. If you could manage to consume 2,000 kcal of lettuce in a day, you will almost certainly gain less weight (or lose more weight) than if you consumed only 1,500 kcal of modern processed American bread.
The problem we face in trying to eat better is that virtually everything you can buy is processed. When you go into a typical American grocery store, about 25% of the outer aisles are unprocessed foods - raw meat, raw vegetables and fruits, nuts, etc. _Everything_ in the inner aisles is processed. Even most of the outer aisle is processed - cheeses, sandwich meats, "fruit juices", etc.
Fiber is a key component to health (and weight loss for those who do not get enough). Raw fruits and vegetables are typically very high in fiber. Processed foods are usually not. Fruits and vegetables are also high in water content. Water and fiber help us feel fuller. It's a bit of an illusion, or rather it's quite temporary because it goes out of our systems more quickly than carbs. Fiber also aids in our gut and colon bacteria balance, and research is beginning to recognize the many roles that bacteria play in our health (including mental!)
The list of reasons for choosing unprocessed foods over processed foods is very long. About the only things really negative about unprocessed foods are their relative higher price and their lower convenience. But if you value quality, then the price argument goes away. Likewise, there are social and emotional benefits to food preparation and meal sharing. So "less convenient" really is just another way of saying "better priorities".