And now I use NetBSD.

systemd also has its own NetworkManager wanna be in the making as well. I also dislike this.

For shameless plug I currently maintain dhcpcd which does your DHCP, IPv4LL, IPv6RS and DHCPv6. Other nicities like carrier detection, SSID and ARP profiles, routing preferences all come as standard. All in 155k. For kicks there is even a basic GTK+ system tray notification widget that also talks to wpa supplicant to allow wireless network selection and password entry.

Gentoo stable requires bash for baselayout-1
Gentoo unstable uses /bin/sh for OpenRC

I know - I wrote OpenRC and maintained baselayout-1 for a long time :)

For pure startup, busybox sh is the fastest, followed by dash followed by bash.
busybox is fastest purely because it doesn't fork as much due to the apps builtin. Plus the apps in question generally have much shorter code-paths due to many GNU extensions being stripped.

I didn't test zsh or pdksh for speed.