Different behavior of watchify and browserify

Is watchify not just a wrapper of browserify?

The two listed browserifyFunction don't handle the source the same. For example the "watchified"-function finds my imports and the non "watchified" not. Why these differences?

```
// Method one: Without watchify
browserifyFunction = browserify(browserifyOptions);

// Method two: With watchify
var options = assign(watchify.args, browserifyOptions);
browserifyFunction = watchify(browserify(options));
```