The most difficult part of measuring using either method is accurately picking the top and bottom of the object due to shadows, obstructed views and the limits of resolution. With practice behavior becomes more consistent, and in tests of measuring with both 3D and oblique images, results are consistently within about 1 meter of each other.

There are measurement tips on these pages:

Measure Length and Pitch on Oblique Content

Measure Area on Oblique Content

Measure Height and Width on Oblique Imagery