Rather that describing diagnosis, in this instance it is the subtle variance of my body sensations and emotions that best describe the differential experience between panic and ptsd.
For me, panic attacks are the feeling of fight or flight, but MUCH more intense. Panic attacks feel like the panic itself is life threatening, like I might die from my current emotions. The panic isn't necessarily related to any immediate stressor.
Frequently in my younger years I experienced panic attacks and developed skills to manage them by realizing that my panic is the suppression of obvious and incredibly inconvenient truths. For instance knowing my boyfriend is cheating but too horrified to let the reality in because of the life altering actions I would need to take if I were congruent with my knowing. I suppress my knowing hoping I can will it away, but the more I try to will it away, the worse the panic.
New to ptsd this decade, the first 4 years after the assaults, I remained so incredibly disconnected from myself I did not feel any panic. I resided just outside the atmosphere occasionally peaking down at myself. I would hear myself repeat the assault stories and defend my obvious damaged behaviors, while at the same time, I was not present with the stories. Kind of like I watch myself from the outside, thinking wow that really seems to upset her (me). I can then immediately immerse myself into a project without disturbance. This state comes and goes for me now.
Both emotional/mental states are disconnected from my trauma, but the denial and suppression in ptsd is far more sophisticated and cunning than any panic attack I've had. It is a disassociation so intense that I don't know it is happening, and I am so tuned out I don't even notice. Whereas I cannot tune out a panic attack, they are completely and utterly consuming.
I am less aware when I am in panic and more aware or hyper-aware when I am triggered in ptsd. I am planning what wall I can climb fastest, constantly evaluating my perceived threat. Panic makes me useless for any actual emergency which is why I now know if I am panicking there is no emergency, because there isn't time to panic in a true emergency. Ptsd brought me an odd confidence knowing, even in my most checked out state, I am the most aware and trustworthy person I know to deal with crisis, attack, threat to my life or the life of my loved ones. My instincts are sharp and ready for action all the time.
Both the gift and curse of my ptsd.