Other than a 80mm will be lighter and more portable than the 100mm.
This is precisely why I would be drawn to an 80mm f/10 scope over a 100mm f/9 scope given my preference for using a lighter mount for greater convenience. But if this is my criteria, my use of this Long Perng scope and the SW 100 as examples may be flawed. To my knowledge, the Long Perng weighs in anywhere from 4.1 kg / 9 lbs (see this post) to 4.6 kg / 10 lbs (see this post) while the SW 100 weighs in at around 3.6 kg / 8 lbs (see this post).
The greater wrenching force that a longer tube would exert on a mount is also something to take into account, of course.