When using any 1:1 macro lens, my understanding is that the framing or field of view remains the same at 1:1 magnification and all that changes with the focal length is the distance at which the you take the photo (i.e. the working distance).
That said, it seems to me that using a long macro lens like the Tamron SP AF180mm F/3.5 Di or the Sigma APO Macro 180mm F2.8 EX DG OS HSM should provide an increased depth of field compared to using a typical 50 mm F2.8 1:1 macro (provided the apertures are the same).
Is my intuition here correct or does the working distance not matter at all?