I think that's a pretty clear answer. More strain variety and if you lose 3 of 9 you still get yeild. If you lose 2 of 4, well you lose more. Myslef i like to grow more smaller plants for those reasons. I can get 2oz every time in a 2 liter pop bottle of coco. Some guys get way more in the same space. 2 gal of coco at 4 plants will get me 8 oz. How many guys can say their 5 gals of soil are going to yeild that much let alone a 2 gal. More smaller plants comes with more maintenance, but it provides variety and morr importantly safety.