I would say zypper up is the better command, just because it's kinda funny. pacman is better overall, but it gets less fun when you start adding arguments like -Syu, if only because it's a "language" you have to learn and isn't self-documenting in any way.
Pacman gets huge bonus points though for having a config option to turn to progress bar shown during package installation into a 'pacman' (letter c) chomping from left to right :)
(done by adding ILoveCandy under the Misc options in /etc/pacman.conf)