You can try it in your browser with this example: https://agviegas.github.io/IFC.js/examples/01/
The main advantages of bringing everything to the client are:
The scalability of the solution. The non-dependence of connection with a remote service to process an IFC means that there could be thousands of users visualizing IFCs simultaneously with no processing cost, since each user would be the one putting the computational power to visualize his model.
The flexibility / ease of use of the library: allows developers who want to use this library to operate without having to mount an API with HTTP calls. A clear example of this flexibility is having been able to deploy the entire application on github pages, creating a basic IFC viewer compatible with any modern device.
There are also disadvantages to this architecture: smartphones have less power than computers or tablets and need more time to parse the IFC; however, in later versions it will be possible to save the processed scene, so that an IFC can be processed with any modern device and viewed with any other, drastically reducing loading times.