The difference between the systems is already clearly explained by the names: 
Monobloc is a single box element and bibloc is a double panel element.

Monoblocs consist of a light weight steel boxes, mostly made of steel thickness
0.6, 0.8 or 1.0 mm. (EPG standard thickness is 1.0 mm steel).
The box elements can be interchanged with other elements due to standized width.
The box elements are closed and cable management and outlets require openable service elements

Bi-blocs consist of gypsum-panel reinforced steel shells, connected to standers or to each other. The steel thickness is normally > 0.8 mm (EPG standard thickness is 1.0 mm).
Each side can be detached individually and interchanged with other surface material panels.
Elements can be opened for cable management and outlets.

Both systems can be satisfactory, depending on the project requirements.
Monoblocs are easier to install, more modular and substantally lighter in weight.
Biblocs are developed to meet the modern requirements of intelligent buildings:
cable management, freedom of outlet locations and adjustable panel surface on both sides. Bibloc partitions are stronger, more rigid and more flexible. Sound- and fire properties are considerably better than monoblocs.

Bibloc                   Monobloc 
Principle                Principle