Fenix for whatever reason only puts the top emitters in the biggest lights, when it's these lower powered models that would benefit the most. That said I don't think Q4 to Q5 is that big a jump. I have the old model (P4?) and haven't been that tempted to upgrade to Q4. If they get up to R4 or something like that, maybe I'd find it hard to resist.
I want a L0D that will work well with a 10440 and retains all modes. I don't care if it is Q5 or R2.
I've got a LuxIII version, two CE's and a Q4. They all seem to work perfectly with 10440 and retain all modes. Do you have one or more that don't work well or retain all modes?