What are the advantages and disadvantages to using an isometric pictorial compared to oblique pictorial in technical drawings

A pictorial drawing represents three sides of an object in a view. An isometric pictorial is a type of pictorial drawing which is built on three lines called isometric axes.Oblique pictorial on the other hand is used to produce two dimensional images of three dimensional objects. 
 Isometric pictorial are usually drawn on pictorial line sheets, this makes things easier when it comes to sketching pictorial drawings. But in using pictorial line sheets one has to determine the direction at which the edge will  be located and the depth that will be befitting for the drawing.
Oblique pictorial use vanish point, which guide the drawer in his drawing, but he has to make some estimations in order to draw a good oblique diagram.

The teacher is mostly talking about the distillation of a mixture

It shows that the experiment is designed properly.