You'll need to consume an extra 250-500 calories per day to build muscle. This will provide your body with sufficient surplus energy it needs to repair and build muscle tissue. It's also important to eat at regular intervals thorough the day.
Forget the fad diet and quick fixes, the only way to loose belly fat for good is via causing a negative caloric intake. That is, either consuming fewer calories than before or burning more calories. But a better strategy, and the best one hands down, is doing both simultaneously - with a combination of nutrition and exercise.
If you absolutely have to pick one over the other, than free weights reign supreme when it comes to quick muscle building. However, to achieve that awe-aspiring physique you need to include both free weights and machines.