Is there a difference between veterinarians when they are listed as either a V.M.D. or a D.V.M.? Is one better than the other and is there more schooling involved?

DVM
This degree stands for doctor of veterinary medicine. People with DVM degrees have graduated from US veterinary schools and earned a doctorate, which is required to practice veterinary medicine. Most veterinarians in the US are DVMs.

VMD
This is a doctoral degree just like the DVM, but it comes from the University of Pennsylvania. The university calls its degree a veterinary medical doctorate and abbreviates it as such.

Other related abbreviations here:
http://www.healthypet.com/Library/animal_bond-23.htm

Apparently, there is no difference in the qualifications. The order of the letters depends only on which school awards them.

http://study.com/veterinarian_training.html