The weight has nothing to do with it.
LEO's formula for determining the "amount" of cannabis one could harvest from a plant is horribly skewed and doesn't take into account how the plants are grown (indoor versus outdoor, soil or hydroponics, etc). Even if you're growing SOG 12/12 from seed in solo plastic cups, if you're busted they will still say that each plant can produce a pound of weed (yeah, from solo cups! I'd like to see that!!) and would be valued at like $3,000 each or some crap.
So, the way I see it, if you're going to grow - GROW BIG. Less plants, of larger size are definitely the way to go.
If your state allows 8 plants, then grow 8 monsters. Size doesn't matter. 8 plants is 8 plants whether they're 2 ft tall or 10 ft tall.