Well if you ask 10 people you'll get 10 different answers. Of the ones I have tried and I haven't tried them all, Surefire and Energizer have been very good primary batteries. It also seems to depend on which light to a degree. For example an Inova X5 doesn't seem to care what you put in it,
the light will run for a loonngg time. Same with a Peak McKinley or a Surefire L1. You may not get high mode but low mode and moon setting last a good long time. I've had a couple KL1's that stayed in moon mode for several hours, easily long enough to find another cell. So experiment a little and see what you like.