As you said, if you can ignore the hunger after eating white rice instead of brown rice...but a lot of people can't (I know I'm terrible at ignoring hunger).

By making diet changes (as opposed to just eating less) one can increase overall health that encourages continued weight control, and general health (which is really what's most important ANYWAYS).

Of course, if someone just hates everything that is diet food, the portion control will probably be a better track to take. Gagging on spinach when you really only like mac'n'cheese and chicken nuggets is a good way to fall off your diet pretty quickly!

In other words...yes, in the end it just comes down to calorie deficits. However it's still important to encourage people to eat HEALTHY, instead of just "less".