Buck drivers can be inefficient, especially the cheaper ones. More expensive well made ones can be efficient. I’ve never felt the need to use the more expensive ones when I have other cheaper options to use. I have never seen where I will significantly benefit much from them to justify spending more.

I don’t just have DD drivers. I have linear/regulated drivers as well. I don’t use any mode other than high in my hunting lights. I have a couple of lights with no driver at all, just a contact board and wires. I only have one light with moonlight, and I rarely use it. My lights are either about how far will it throw or how big of an area will it light up full throttle. I have numerous liner and DD drivers with guppydrv on them but they typically stay in 100% mode only. The only lights I use in other modes are the ones I keep around the house that rarely get used.