Brightness: How bright of a flashlight needed is another key factor when deciding which flashlight you need to buy. If it is really dark where you work, you may not need as bright of a light, whereas if you are in a semi-lit place, you would need more brightness for greater contrast. Flashlights can vary from 1 lumen to as much as 3,000 lumens! Lumens is the measurement of brightness the flashlight has.
Size: Size plays a big role in picking the right flashlight for you. If you will be carrying all day, then a nice light pocket rocket of a flashlight would be ideal. A flashlight with a bigger head will be more powerful yet there is additional weight.
Batteries: This is often a key factor that gets overlooked. The new high end flashlights generally use CR123 or 18650 batteries. These are much more expensive yet they provide tremendous power to the flashlight. Some people prefer a flashlight with rechargeable batteries, while others like the convenience of having a flashlight that takes very common, easy to find batteries, such as AA or AAA.