Shaman: 10% more cast spd with Staff, and an staff=m crit rate and dmg, in general, plus double hit, m crit, etc procs
Cleric: 10% more cast spd with mace=m crit rate (but just in the dps ones), wis, and some defense or lowering resist
For shaman, u can put knownledge in case u want even more wis, but tbh, no need to waste points on it, having all the rest of gear is enough.
As a player stated before, they have different play styles, so they aren't really comparable even being in same branch, at least for me.
So, the 2 are equally good, depends more of how u gear and play them.
This chat reminded me to something that happened with a player in EE ES forum recently, the guy thinks thief is the best class ever... but no class is the best, all are pretty balanced and depend of who, how and with wich gear is using them