Ok then, now that I know the runtime of an L2i with R5 drop-in on AAA's (thanks ChibiM) the next step is to understand whether the Solarforce or Trustfire R5-A3 is the more powerful torch.
I'm assuming that the Solarforce will win because it has a bigger reflector, and is supplying 3.75v compared to 1.25v from the Trustfire?
I'm a total novice at this so shoot me down if necessary!