Downsides of scrog (why i dont scrog):
1) In limited grow spaces, it is impossible to get to all the growth tips you need to be able to get to all the plants.
2) Hassle of building a base attached to your grow tank/pots so you can easily draw out the screen and plants as one. This is VERY important unless you want to spend a year clipping the screen out at harvest with wire cutters.
3) Hassle of training.. a good scrog will require many hours work and a relatively perceptive and dedicated grower.

But the advantages of increased yield beats the shit out of the negatives