As a soldier in the reserves for over 4 years I see the difference between Civi PT's and Army PTI's All the football clubs and sporting teams normally mimic a lot of there Pre seaon training on Army models.
My recomendation. Join the reserves as a PTI get smashed in fitness and learn how to inflict hell on people. THen when you start your own business you are different from the rest of the PT's out there. You have military experience and that goes a long way.
Negatives: You will be put through a very gruelling few months of courses and training, You get beasted by crazy PTI's, blah blah blah
Posatives: You are serving your country and doing something honerable, You get an awesome life experience, you get tax free pay, see the country, People respect your training
This is just my thoughts and the PTI's that I know who are army have an awesome clientel. They run boot camp style training and people love it......
Peace out