What form of therapy is most beneficial for veterans with Post-Traumatic Stress and why? what are your thoughts on Group Therapy?

I don't believe one form of therapy is "best" for all. Different people have different needs, and have had different experiences. Quiet solitude can be helpful at times; having a trusted friend to listen in a nonjudgmental way can be equally beneficial. Bottom line: do what lets you relax.

My take is that you can't assign a one size fits all. Every veteran is unique and every story is unique.

The one commonality, though, is that the veteran MUST be committed to working on their PTSD for the long haul. Seeing a Psychiatrist (or other prescriber if a Psychiatrist is not available), seeing a therapist, groups if assigned, meditation, medication, etc, are all part of it. As are doing things in a controlled manner to go outside the comfort zone...

If the veteran isn't fully invested, they won't ever recover...

As someone who works with service members living with PTSD on a daily basis, IMHO there are different therapies that work well to address the symptoms of PTSD. Here is my list of therapies I would recommend to someone living with PTSD. There are others, these are the ones I have seen first hand work.

1. Prolonged Exposure Therapy (PE) this is one of the most intense treatments available for the symptoms of PTSD. It works well for emotional concerns such as anger, anxiety, and guilt.
2. Cognitive Processing Therapy (CPT) this therapy requires a good majority of work outside of the therapy office. It works well for painful thoughts and behaviors.
3. Acceptance and Commitment Therapy (ACT) this approach is innovative in that it does not seek out to eliminate the symptoms it seeks out to utilize values to produce a fulfilling life experience and feeling better is a byproduct of living well.
4. Any of these treatments in a group setting increase their effectiveness.

PTSD is an anxiety diagnosis and perpetuated by a system of avoidance. Avoidance works in the short term. However, over years (7-12) the avoidance stops working and a persons life is restricted to only a few places and only a few people and a few emotions, mostly anger.

I would like to leave two thoughts here for others to consider
1. A memory is not something that can be deleted, medicated, or forgotten. It is also not 3D and can not kill you. If your goal is to get rid of the memory therapy may not go the way you want it to. If you go toward treatment looking for a new meaning to the event any of the aforementioned therapies will work well.
2. A persons willingness to go towards this painful memory/experience stands in direct conflict with the avoidance that keeps PTSD alive and well in a person. The question then becomes can you have this painful event in your life and still live a full and satisfying life with it.

remember, What gives light to the world...must endure burning --Viktor Frankel