When comparing systemd vs Upstart, the Slant community recommends Upstart for most people. In the question“What are the best Linux init systems?” Upstart is ranked 6th while systemd is ranked 7th.
Ranked in these QuestionsQuestion Ranking
Pro Cgroups processes control
Systemd groups all processes by services using Linux's cgroups. Think about memory/cpu/tasks/IO/Net limits and accounting for any service.
Pro Login management out of the box
Systemd contains a daemon called logind which is used for managing user logins.
Pro Default for many popular distributions
Systemd is the default init system for most popular Linux distributions (Arch, Debian, Ubuntu, openSUSE, Fedora, etc.) Therefore there is an insane amount of support behind Systemd. Choosing Systemd means running with the herd, which comes with it's pros and few (or none for some people) cons.
Pro Free and open source
Pro GPL Licence
Pro Full use of kernel features
Pro PRO doesn't cripple your hardware
Instead of assuming your computer is a static machine, systemd is designed with modern computers plug and play design in mind.
Pro Backed by Red Hat
Pro Easy to manage
Pro Easy to understand
Pro Simple .conf file in /etc/init
Pro Event based startup was fantastic.
Since it is event based, it was simple to have interdependent services emit status messages each other. Service start ordering and shutdown was easily managed in one conf file.
The "lazy" start of systemd is BS and is a mess to debug . service unit files have no clue what another service state is. The maintainers add arbitrary timers that add more complexity and more init hangs. The systemd documentation is poor. When a service fails to start (or stop) systemd follows the Microsoft model of not telling the reason why.
Con UNIX-like isn't the same as the UNIX philosophy
One of the main argument that people who are against using systemd is that it does not follow one of UNIX'S core concepts: 'Do one thing and do it well'. Instead, systemd represents a collection of dozens of tightly coupled libraries, with responsibilities that exceed those of a simple init system, since it also tries to handle things like device management, power management, mount points, cron, encryption, syslog, network configuration etc...
Con Makes dependent products difficult to port
Software dependent on systemd. Becomes difficult to port to systems that lack systemd.
Con Too monolithic
It tries to do too much - most people who use systemd aren't even aware of most of the features and don't really use them. It makes can be with complicated to deal with, and it's possible that in a few years this project will be a nightmare to maintain, and the users will feel the effects.
Con Binary logging
A binary log structure means that any tools you want to use to parse it will have to be aware of its format, and know how to deal with the ways it can become corrupted. Otherwise, it's not really possible in the easy sense.
Con Runs only on Linux
Con It's all or nothing
While it is technically possible to use software without SystemD, it really is true that it is "almost impossible" to use software without it, given that all the hard porting work to other init systems has not been done already for you, or given the fact that you are trying to install unported packages directly from the authors (either from binary, like a DEB file, or from source.) Consider the following:
Every major Linux distribution runs SystemD as an only option for init systems.
Around %95 of GNU/Linux users use SystemD, give or take.
SystemD makes things easier for lazy developers (at a cost, however.)
Therefore, most software packages that depend on an init system are developed with inherent and sole SystemD support, in favor of the status quo. While distributions such as Artix-, Gentoo-, and Void Linux have been able to correct packages that depend on SystemD, it is not the easiest to do so. Developers and users wanting to package their own software or build software from source may give up trying to work without SystemD since the software may need to be edited for extra compatibility.
Con Connects to Google DNS servers by default
Con Overkill as an init system, resulting to unsafe init system
1.2 million code lines...
How this monster is controlled with such a huge size, for security leaks and other aspects?
How about if, the homed new service fails and your home folder may become unreadable or useless?
Con Need glibc
Con Frequently change APIs
Con The new version does not consider backward compatibility
They just remove the features they think are "incorrect".
Con Low-quality code
Con Kills background processes after the user logs out by default
Con Aggressive marketing
It's trying to deprive people of freedom of choice.
Con Makes maintaining a hassle
Con Lead developer shows near complete lack of care for standards of quality needed for developing a part of an OS as integral as the init system is
Con Ubuntu abandoned it
The original developers (Canonical) seem to have abandoned this project. At least they're no longer using it in Ubuntu.
Con It was just sysvinit or systemd in disguise
It really just offered a barely more intuitive way to create init scripts for the actual init system running behind upstart.