IMHO, path is far better preparation for dermpath. Learning about pathology of other organ systems, differing histologies, etc, "training" the eye as a pathologist over a several year period may make the task easier. Who would I rather have looking at my biopsy slides? A pathologist. For things like skin cancers it isn't that important, but for vasculitides, reaction patterns, bizarre inflammatory conditions, and lymphomas, I would rather have the trained pathologist's eye. Of course, the whole point of doing a derm path fellowship is to understand this and learn it, so I have no doubt that there are many with dermatology backgrounds who excell at this. It's just a general gestalt I have.
Of course, coming from a derm background provides the clinical advantage of understanding why lesions are biopsied, what the clinical differential is, what a descriptive term actually means, etc. Although good fellowship programs will provide you with this as well.
As for which is "easier" I have no idea. I think it probably depends on how many people are applying and what background they are from. Traditionally, I believe pathologists tended to apply more frequently than dermatologists, hence perhaps easier for the occasional dermatologist to get in. Now, this may be quite different and I think there are lots of derm folks trying for a spot.
As with everything, it probably depends on who you are, who you know, and your resume.
It also depends on what you want to do. If you just want to do dermpath, than why on earth would you do a clinical residency? If you want to see patients, then obviously the clinical track might be a better idea.