I went with the 5's this second time because last time it was a freaking nightmare transplanting from 3's to 5's! This time I'm doing everything I can to keep them from getting stressed! Had two hermis in a smaller space.
Now I have a 9' x 5' space and four of them are taking over in 2 months at 24 hrs. In 2 more months the space WILL be filled I'm sure of it... the stalks at the base are 3/4 inch now!

Go with the 5's!
Good Luck!