An institution with a civilian student population will be significantly less "military" than one that does not. This is a benefit for some, and a drawback for others. Every organization has nasty individuals. How you deal with the people around you is up to you.
As far as the physical demand goes, that will depend on you. You will have free time. How you spend that free time is up to you. If someone has to make up mandatory PT in order to get you outside for exercise, you might want to reconsider your career path. If you want to take academic internships over the summer instead of going to military schools, that is your choice.
Comparing equipment and facilities is nice and all, but will you be the midshipman/cadet that actually makes use of those facilities? Or will you make a 2.5 and never come close to doing any independent research? Will you spend four years in a "leadership laboratory" only to follow the leadership of others, only pointing out where the strong man stumbled and where the doer of deeds might have done them better?
Simply going to a military school, a service academy, or enrolling in ROTC will not make you a successful officer. That responsibility is yours, and yours alone. The degree is a piece of paper. The officer and leader is you.