I've never tried Panasonics, but I've used Sanyo, Surefire, Energizer E2 Lithiums and Duracell Ultras. Most of the time I go with Duracell Ultras, but Surefire has the best deal on their batteries and they are just as good. The only experience I've had with Tekcells was when I got my Pelican M6. It came with Tekcells and they were the crappiest batteries I'd ever seen. They produced an awfully dim yellow color to the M6's beam so I soon replaced them with Duracell Ultras and there was quite a difference! With the Duracells, my Pelican was nice and bright.