About speeds, systemd shuts down faster than anything else. No doubts. But at boot it depends a lot on specific systems, what and how many services you launch, the hardware, etc... Simple systems (the ones I tend to use) into decently powerful machines don't use to see a specially noticeable improvement with parallelization. I've tested some systems with all equal excepting inits. Even the plain sysvinit with no OpenRC is very fast and not far behind systemd. Only slightly slower. For complex systems that's a different story. systemd and/or parallelization in general can speed up booting times a lot.
In my particular case booting speeds are not relevant. Doesn't make a significative difference whatever the init system you use. At least the ones I've tried. There are plenty available not specially known.
