If growing outside then you definanately want to top, trim, and supercrop. I know that many will say don't do it, but just try to check your colas for mold or bugs on a twelve foot plant without having to buy an orchartd ladder
. I know because I now have 2 haze plants that are above 12 foot in height and they are a real pain to service. I broke the tops on one trying to bend it down to check it out, not good.
That being said, if growing indica dominant plants, it's not so much of an issue as they tend to bush naturally anyway, but sativa dominant varieties tend to grow more like a christmas tree and reach for the sky with one central stalk and main cola.
The only reason I didn't top/trim the two sativas was on the advice of a 'friend' who claimed to have grown the same strain as I have. Free advice is sometimes worth only what you paid for. I will now top and trim ALL plants that are going into my outdoor grow that have ANY sativa in their heritage.
As an example, I have 6 Mr. Nice ( Indicas ) that I didn't top and they are all nice round bushes that stand 5 to 6 ft. in height and equally large in diameter. As opposed to my sativa dominants that I didn't top that are 8 to 12 ft. tall without much in the way of side shoots.
Another advantage to topping is that you elliminate that one big central cola and exchange it for multiple smaller colas. This is an advantage because the larger colas tend to retain moisture and are more subject to bud rot and other problems than smaller colas are.
This is important if you live in an area that has a high humidity or is subject to a lot of airborn moisture, like fog. The Pacific Northwest and coastal California comes to mind as places that growers are constantly battling mold and fungas problems. Smaller colas will dry out quicker than those hog leg monster colas.
Thats my reasoning anyway.