You missed a bit: it's not just that sysvinit is small, it's also that it's almost maintenance-dead. Thus, it is highly unlikely that it contains significant unknown crash bugs. systemd is relatively new and rapidly changing, so its probability of containing unknown crash bugs is much higher.
I treat init like filesystems, and don't use inits that are still changing a lot or only a few years old for anything important. systemd still falls into both categories. In time, it will emerge from them and become mature (i.e. closer to dead :) ) and thus safe to use for real work in the view of paranoid maniacs like me.