How is Langmuir adsorption isotherm different from Freundlich's? I see no difference between the two. Both say that the degree of adsorption reaches a limiting value at high pressures and at very low pressures degree of adsorption is directly proportional to the pressure.
Where does the difference lie?
There is a fundamental difference between both models.

Langmuir's model was a theoretical construct, while the Freundlich isotherm is empirical.

In the Langmuir model, it is assumed that at maximum coverage, there is only a monomolecular layer on the surface. This means that there is no stacking of adsorbed molecules. The Freundlich isotherm does not have this restriction.