IME it all boils down to what you want to do. You can get the very best out of your plant in whatever pot size you choose, there's no magical pot size that will suddenly give you the best out of it. I use 4 x 6.5L square pots in my 'drobe, which allows me to grow up t 4 strains, whereas using 2 x 11L squares (which would probably yield about the same final weight I suppose) would reduce that choice.
I used to grow all my plants in 10 and 15L buckets. But then I read OT1's
"48 baby cuts" thread and saw the potential for scaling down. Made sense to me, because it meant less hefty lifting and with my back, that's good news. I've never looked back. Since then I've grow in whole rooms, partitioned rooms, big boxes, grow tents and now my little wardrobe. The 6.5L Squares have proved perfect for every situation.
There's really no need, IMO, to go upwards of 6.5L squares in an indoor grow. They are so easy to use and even with dodgy old spines like mine they are perfectly liftable. I've had strans that can produce 2 Oz off a 36" (finishing height) plant, which would mean that if I did that x 4 in my wardrobe I would end up being within a smidgin of the 1 gram per watt target. Given better growing skills, I am sure that target could be passd with ease.