IMO strength is a skill. so more often would be better. so according to your choices every 5 days is the option to take.
i still feel you can make size gains on even more frequency, like twice a week. as long as you use 2 types of workouts, a higher volume workout and a lower volume more intense workout.
some could day 3 times a week would also work, for example the texas method does it and does it well. but lets not complicate things when you seem to think 5 or 7 days are the only options.