I'm in a similar boat, except I am already 22 weeks pg and my traumatic birth was a hospital birth. I am currently figuring out how to make a birth plan that addresses my concerns, and it is difficult because I keep bumping into traumatic experiences that I'd prefer to avoid.
Anyway: the main reason for my traumatic birth were medical interventions, being ignored by doctors and hospital staff for hours, and miscommunication/dishonesty when the OB finally did show up. Needless to say, I am still very angry about my experience even two years later, and my goal is to have a different experience that is more affirming for me as a person.
My plan: I will birth at a hospital again (no choice; there are no midwives in driving distance in my neck of the woods). I have considered even using the same hospital (chance of getting the same OB is 1:7), but since they don't VBAC, I have since rejected that idea. Instead, I am looking at a hospital 30 miles from here which has a great reputation. It is important to me that my provider will know where I am coming from, so my medical record actually states that I suffer from birth-related PTSD, and hard as it will be, I have to discuss this with my new birth provider. I will request that during the birth I will see nurses and docs regularly and that they will have to inform me of the progress. I will also request that any interventions or complications will be discussed entirely and honestly with me and my husband and any other person I choose to attend the birth. Needless to say, I will again push for a natural birth, and keep interventions at a minimum, etc.
Your situation: How about consulting with professionals involved in both options. Do you research on who they are and what they require you to do? Remember that you can keep your options open throughout your pg and that you can change your mind if it seems necessary.