When comparing F.lux vs RCDefaultApp, the Slant community recommends F.lux for most people. In the question“What are the best power user tools for macOS?” F.lux is ranked 26th while RCDefaultApp is ranked 69th. The most important reason people chose F.lux is:
Helps provide better sleep for more energy during the day.
Ranked in these QuestionsQuestion Ranking
Pros
Pro Can help sleep better
Helps provide better sleep for more energy during the day.
Pro Eases eye strain
Decreases color temperature at night, changing the normally fluorescent blue of an LCD monitor to a soft orange. Much easier on the eyes, especially in a low-light environment.
Pro Subtle transition
The transition from daytime to nighttime color modes takes an hour by default and will detect your current timezone, meaning that it will happen in the background at sunset, often without you noticing.
Pro Provides missing functionality
Standard features on Windows, but not on Mac, this fixes that.
Cons
Con Takes a while to get used to
After installing F.lux, the screen will look a lot more yellow. This takes about a week to fully get used to. You can ease into it by setting the color temps higher than the recommended defaults.
Con Last update was in 2009
But the software still works, so far no issues on El Capitan 10.11.3.