Depends on your goals
Both...only time a workout isn't beneficial is if ur messing around or just plain dnt knw wat ur doing...
I do 30-40 minutes I get through my workouts
I try to keep workouts less than an hour. After an hour, testosterone levels drop and benefits minimize. Pick 3 to 4 muscles and work them out in an hour, using different exercises and tempos. You can kick your own ass in one hour