Any Mag-light is top quality, that said, C-cell or D-cell is pretty much a matter of choice as far as wt./size is concerned. Having seen 6-C and 6-D both in a dark room, I think you'd need to use a meter or gauge of some kind to tell the difference... keep in mind, when they first came out, they were purpose built to stand up to a LOT of abuse and to double as a club. They are heavy, but if you keep fresh batteries and a good bulb in them, neither one will let you down.

Troy