They both have that mental factor too and the psychological. Its a huge test to get somewhere in both but once your done then the real test is staying alive.I don't think they even compare . Both are physically challenging no doubt but to be in the military is a whole different thing.
Like the military the police academy involves handling stress to a high level. If you cannot handle stress then its not the job for you.I guess the police academy is easier than the military, specially for people that want to follow a career in the military. Both are challenging but there's no comparison, in my opinion.