best battery to use

i have a hand held laser (200mw) it runs on 2 AA's but what would be A better battery life energizer lithiums, or energizer rechargables?

Lithium primaries run the risk of killing the laser. They deliver something like 1.8V when full. The rechargeables are likely NiMH, which provide only 1.2V but don't sag under load as much as alkalines.

I always ran my Optotronics 150mW off of a pair of NiMH's. I traded more initial power for more uniform power over the life of the batteries.

Plus I didn't have to keep buying alkaline primaries.

-Trevor