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Strictly in terms of DOF, a 50/1.4 lens will have less DOF than a 105/2.8 at equivalent subject magnification, for all subject distances.
However, one can go further and state that the extent of background blur is nearly always greater with the 50/1.4, at equivalent subject magnification and equivalent subject-to-background distances. For small subject-to-background distances, the blur circle diameter is approximately twice that of the 105/2.8, with the difference decreasing with increasing subject-to-background distance. When this distance is very large, the 105/2.8 has approximately equal background blur.