Nursing school is definitely mentally challenging. But, there are alot of factors to consider. Are you going to NS full time, working full time and have a family? If so then NS is definitely harder.
However, ask a nursing student to wake up at 0545, PT formation at 0615, if your luck run for only 3 miles, then report to work 0800(police call, clean weapons, class, gun team) go to lunch for an hour and half (nap), go back to work(clean weapons, working party, class, gun team etc), working party up, police call, 1630 formation, police call, field day, oh by the way devil dog you have weekend duty.....and then you get to do it at least 5 days a week if your lucky.
Like they always say, don't let the green grass fool ya.