It might be worth one's while to consider the relative power outputs of the various races when debating the subjective "efficiency ratings" of their weapons- klingon power planets put out roughly 80-85% of the equivalent fed one, roms are around 90-100% of fed warp core output...polarons, for instance, while they utilize 1 less point of power than the advanced fed torp, the quantum, the polaron is a greater relative stress on klingon power systems; this also somewhat diminishes the overload potential of k-photons (still well balanced against f-photons though).
The numbers posted thus far heavily weigh damage-over-time, which does have some serious weaknesses to consider: first, just because a weapon that can fire more often, does not mean it will always be in position to fire as soon as it is ready, and even if it is, it may not be hitting the same place (relevant to shielded targets), so that the actual damge being done over time may often be short of the full potential of the weapon. Another thing to consider as well is the fact that crunch power isn't really considered in these figures- weapons dependent on doing damage over time naturally tend to have less punch per shot, but the big, slow weapons can often take a shield down and do significant hull damage in one salvo (which might especially such if the ship with fast weapons has a bunch of it's weapon systems damaged/destroyed/stunned). I have to admit though, I don't have much of an idea on what would make a good formula for computing a useful "crunch power" value for weapons (plus it wouldn't be much value when considering the borg as one's target, after all, they haven't got any shields).
Just a couple things to consider when one looks at those efficiency numbers.