Reel capacity is more for trolling rods. That would never be a factor for casting rods.
When I said degrade, I meant that from a fishing stand point, not biodegrading in the environment. Braid won't be junk from sitting in the sun for a few weeks like mono would. I change mono pretty frequently, I have yet to change a spool of braid for any other reason than wanting to try something different.
Lines with little stretch are better for structure fishing, you can feel bottom, rocks, brush, or tree limbs much easier. The actual strike is much easier to detect as well. Fishing brush with mono, sometimes I get excited and sink the hook into a limb, with braid/nanofil I can easily tell the difference between something solid and a fish. Makes working a brush pile much less frustrating.