Ranked in these QuestionsQuestion Ranking
Pro Very stable
Since sysvinit does only one thing (initialize the system) and one thing only, it's very stable and it's impossible for it to fail for any problems unrelated to booting the system.
Pro Simple to understand
Con Can lead to slow boot
Since init starts tasks serially, it has to wait for a certain task to finish in order to start the next one. But when startup processes end up I/O blocked, this leads to considerable delays during boot.
Con Launches a bunch of processes to launch a process
Every init script spawns at least sh/dash/bash, and probably also additional processes such as cat, echo, start-stop-daemon, etc, just to start a single daemon that may not even be needed at the time of boot. This massive overhead results in poor performance, and is a killer for embedded systems.
Con Duplicated implementation for every service
Every init script needs to reinvent the wheel for every script: argument processing, start/stop/restart/reload/status/whatever processing, finding/clearing/creating PID files, sourcing defaults, building and setting configuration options, so on and so forth.
Con Initscripts is not portable
It is virtually impossible to write portable sysvinit-scripts
Con Hard to write sysv-initscripts
As one needs programming skills (opposed to a declarative style).