Procedural and Dermpath fellowships are more competitive than Derm residency because there are so few spots. In Procedural Derm, there are 45 ACGME accredited programs. In Dermpath, there are 54 ACGME accredited programs. Most of these fellowship programs take only 1 fellow a year (although there are some programs that take 2 or more fellows a year).
http://www.acgme.org/adspublic/
Additionally, virtually all people applying to these derm fellowships already have outstanding CV's/resume's, grades, and USMLE scores (they must be great if they got accepted into a Derm residency). Hence, the competition is stiff.
Procedural/Mohs Derm fellowships have always been competitive. I think this is because it tends to pay well after fellowship and offers some additional training in cosmetic procedures (liquid cash procedures with no hastle of insurance). Dermpath fellowship competitiveness seems to change from time to time. Dermpath is currently very competitive today. But a decade ago in early 2000's it was much easier for dermatologist-trained person to get in. Dermpath trained dermatologists are also well-compensated in pay.
I've been accepted to a Dermpath fellowship. I have multiple friends who have been accepted to all derm fellowships - Procedural, Dermpath, Peds.
My recommendation is do a derm fellowship (Procedural/Mohs, Dermpath, Peds) only if you really enjoy this subspecialty and can see yourself doing it every workday. Do not do a fellowship for the money (because this is a waste of time for you and the fellowship program training you).