The considerations about the relative importance of x-risk reduction seem to be fairly insensitive to 10^-1 or 10^-5 (at more extreme values, you might start having pascalian worries), and instead the discussion hinges on issues like tractability, pop ethics, etc.
I think differences over that range matter a lot, both within a long-termist perspective and over a pluralist distribution across perspectives.
At the high end of that range the low-hanging fruit of x-risk reduction will also be very effective at saving the lives of already existing humans, making them less dependent on concern for future generations.
At the low end, non-existential risk trajectory changes look more important within long-termist frame, or capacity building for later challenges.
Magnitude of risk also importantly goes into processes for allocating effort under moral uncertainty and moral pluralism.
I think differences over that range matter a lot, both within a long-termist perspective and over a pluralist distribution across perspectives.
At the high end of that range the low-hanging fruit of x-risk reduction will also be very effective at saving the lives of already existing humans, making them less dependent on concern for future generations.
At the low end, non-existential risk trajectory changes look more important within long-termist frame, or capacity building for later challenges.
Magnitude of risk also importantly goes into processes for allocating effort under moral uncertainty and moral pluralism.