The downside to metal water bottles in desert climes (for everyday use) is that if you leave one in your trunk or car seat during the day, its a burn waiting to happen when you go to pick it up. While solar heating is unavoidable, at least plastic bottles won't burn your hand when you grab it. Minor observation on long term ubiquitous use.

Of course we're discussing off grid use. I prefer 'Nalgene' bottles to hydration reservoirs b/c even though the bladders carry more I don't drink as much and works better with my SteriPen and tablets. YMMV. (I do use a reservoir when I run).

Let me try to explain my hiking style and maybe that will help this make sense. I don't tend to heat water from fire.
--I have a Jet Boil, very easy and cup provided.
--I have a White Box Stove that I use a UL 3 cup teapot. A bit bigger footprint in my pack but its still a lighter set up than the Jet Boil.
--I just bought a GSI Halulite Minimalist cook set for $22 which would be the closest I have to being able to boil water on a fire. It nests a 1L Nalgene bottle perfectly and weighs about .5 oz. It has a rubber two finger pot gripper that is pretty ingenious.

I would always prefer to boil water w/o an open fire, and guess now I can.