When comparing MacPorts vs F.lux, 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 25th while MacPorts is ranked 51st. The most important reason people chose F.lux is:
Helps provide better sleep for more energy during the day.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Provides a consistent experience across OS X versions
MacPorts eschews Apple-supplied libraries and links sources against its own making sure that the experience is the same regardless of what OS X version is used.
Pro Generally very up to date
MacPorts generally gets new software soon after it's available. This way users will not have to worry if their software is up to date.
Pro Nice variants system
MacPorts has a variants system that allows customizing builds with author provided options.
Pro Fast
Written in Tcl & C, it's generally significantly faster than the competition. Tcl is also quite readable and comparable to Ruby, so it's also friendly to newcomers.
Pro Has many more packages than its competitors
As of this writing, 20K packages. 3 to 5x more than other current package managers.
Pro MacPorts is a native application: C + TCL
No need to install Ruby, or any other programming language.
Pro Requires SUDO to install apps
No need to worry if some rogue app will change your binaries or configuration.
Pro Most of the available packages work
For example, trying to install Finch using Pkgsrc doesn't work, while installing it using MacPorts works perfectly. Finch isn't even on Homebrew's radar.
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.
Cons
Con Bad at limiting dependencies
MacPorts has a habit of pulling very specific versions of dependencies for each package. It downloads different version of already existing dependencies even in cases where the existing dependency version would have worked seamlessly.
Con Downloads unneeded libraries duplicating functionality already provided by Apple's libraries
As MacPorts eschews Apple-supplied libraries and links sources against its own a large duplication of functionality across MacPorts and Apple libraries can be found.

Con Requires root permissions (sudo) for installation of packages
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.