Thread: Replacing headlight batteries

Hi all. Hoping to get some advice about rechargeable batteries. I have a couple of rechargeable headlights here with buggered batteries. One is a led lender h7r signature and the other is a Fenix hm65r. Looking at replacement options online, the led lenser 21700 batteries are twice the price of a lot of the other options. Is there any reason why I need to stick to the same brand battery as the head torches or will all 21700 batteries function the same?
Thanks