I have no SOG or SCROG experience, but I do use a Mylar tent with limited space, so I'd imagine SOG would give you the best results since you're using 6 inch pots. 18 plants can be packed into your tent and get enough light exposure on the foliage to give you nice buds.
From what I see with a few SCROG setups, many growers leave a lot of foliage under the screen, out of the path of the light. That is actually wasted light, because the more light that shines upon the full surface area of the leaves, the more "energy" going to flower production.
Fewer leaves exposed = Less energy for the plant?
If you SCROG it, it will take more time for your plants to grow out and fill up the screens, so the SOG would allow you to harvest faster, without sacrificing quantity.
But then again, that's just my $.02!