An extra little factor to think about is the changing of batteries.
Just suppose that you were using a small flashlight that uses two AA batteries, and suppose it just went dead on you. You fish around and find two new batteries in your pack. Now you have to open the flashlight up, pull out the dead batteries, figure out the correct orientation of the new ones (by feel), then slide them in and close the flashlight case. But you have to do that in the dark! With some flashlights, this is a royal pain. With others, it is a breeze. When you get out of AA or AAA batteries and get off into type 123 batteries, it gets harder. When you get off into button-type batteries, it gets harder yet.