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I would use organic when I have awkward shapes with overlapping areas. The branches allow you to support overlaps without building support structures directly on the lower parts. It can also be more material-efficient if you need a lot of support.
Snug I would use if I need better support on larger overhangs or long, thin areas that are likely to sag otherwise. It's also better at holding up parts that could detach from the build plate under their own weight as you would generally have the support along the surface as it builds up, whereas organic usually only contacts the print at the exact support point. Snug supports are generally pretty easy to remove and clean up.