Not sure what this means. Certain weapons give additional Power (Longsword) or have other dmg production means (Sickle creating more Skull gems, twinblade increasing crit output), so these do potentially decrease match time but it can just as easily contribute to overkill. Damage output is the same for all weapons at all rarities at all levels, ignoring Abilities.
The primary means to stun (a complete row of matched gems) is chance-based, since the production of gems from mana-producing spells is random so the possibility exists that a stun will not result even after all spells are cast and gems are manually matched. What are the other consistent ways? Blackjack? Nice if you are an assassin, but still chance-based. Poison Spirit? Still chance based and basically the same odds as Hammer provided you are running green spells. Cockatrice Juju? ok, not chance based but have fun running a Blue Shaman. The benefit of spells over the hammer is that you know if the enemy has been stunned before moving to the gem-matching phase. But they are not necessarily more consistent than the hammer, just different timing.
The reason why the Hammer in my opinion is the best weapon is that most people playing the game currently do not have @Tacet’s gear options. For many, being able to complete the highest difficulty Challenges is most important, not decreasing match time by 5% or more by adding additional damage. Having the most stun options is valuable in that sense and is most useful by all. Having both barrier and stun running as options means that you can choose in any given turn whether you have to be careful or can choose more risky maneauvers (perhaps you have barrier in place, but weren’t able to complete a full row-match stun, and then Hammer triggers, you still have barrier in place for the next turn to have more freedom to take actions and more likely not get one-shot in the middle of a long dungeon Challenge run).
TL;DR: I value board control more than damage output when recommending an all purpose best weapon. Obviously Mastery (color) matters so a Green Dwarven Hammer is less useful to a Paladin but that is true of virtually all weapons.