What Tempurate is better?

What makes it more powerful and efficient?​

Cold temperature, like outside
OR

​

Warm,like room tempurate

That depends on a whole bunch of factors and varies from laser to laser if you're talking about green laser pointers.

Crystal alignment, diode frequency, pump diode power, power stability, and temperature all come in to play when determining power output, stability, etc.

For me, cold temperatures (e.g. winter air) does not go well with green lasers. If I want to use them outside in the winter, I have to put them in a pocket to warm them up.

It seems like temperature affects the batteries more than any other part of the laser.

It depends like mentioned before, but most are geared towards operating at room temperature.

Batteries, especialy NiMH's, have problems with really cold temperatures, which is an issue unrelated to the actual laser. Most green pointers will not operate at cold (freezing) temperatures even if supplied proper voltage from a lab supply. This is mostly caused by the pump diode frequency shifting upwards in the cold, and becoming incompatible with the absorption band of the solid state laser.