If you don't know what you're talking about, don't talk. The fenix L series are all regulated, running the LED at equivalent power no matter the input voltage (within reason). There is NO difference in brightness between fresh alkalines batteries and NiMH. There is a difference with a MM, because they're poop, and there is a difference with the fenix later on, because alkalines are poop.
I know another phase that goes like this- if you can't speak politely, don't speak. I read the site to learn from people who know more than I do- and you are someone who knows more than I do, (about things other than manners, that is.) I am glad I learned this from you- I didn't know I had it wrong.
Polite discussion on this site is one of its great draws. Using courtesy in your tone will also add to the number of new people, like me, who join to get a better understanding of the flashlight as both a hobby and a tool. If you don't have interest in sharing / educating people, perhaps you should start an expert only site.
Thank You for clearing up my misunderstanding about voltage of battery / overall output.