Building materials decisions can be driven a lot by local availability...freight becoming more of a cost factor. Other considerations, like span distances, and environmental issues like moisture, also take a role.
We build a lot of what you would consider smaller sheds, since we do not need or want big row cropping machinery, and a commonly available 16- foot Southern Yellow Pine rafter is a locally- sourced, strong framing member that we default to for most rafters. Ditto for pressure- treated posts.
Our primary concerns for weather are with hurricanes, which gives our county a wind load zone of about 100 mph, sustained, or perhaps a little more. We reinforce with hurricane strapping on every rafter.
Of course, one thing hurricnaes often do is spawn tornados, too. I agree with Nebrfarmer...a tornado takes whrift wants wants, often droning enough damage that a total loss of a structure is easier to work with, than trying to repair one.
Beyond that, our snowfalls are seldom as severe as what most of you deal with, but we can get a foot to 18 inches in a day, once in a decade or so. We have to allow enough slope to deal with that, and also ice storm weight, which is often worse.
We have pole sheds with treated posts and metal roofs and skins that are forty and still going strong. I am more concerned about premature corrosion I see in some metal elements we buy, which may be imported, than I am with a good pressure- treated pine post. I have some expensive storm doors on my office that haven't lasted five years, and they are riddled with holes, so are being junked.
We pay attention to buying a heavier gauge metal for roofing, and use longer fasteners, to handle wind loads. I have had one roof fail in forty years, and it was attached to a building someone else designed and built, which was the weakest link.
If you are using your regular labor pool, instead of hiring a contractor, doing with what your people know how to handle, can create significant savings. I know how much slope they are comfortable working on top of, and how much weight they can easily hoist to form a plate...stuff like that. Everyone to their own best way...
