By "shingles" do you mean little strips of wood or those bitumen sheet thingies, keeping in mind I've never lived in any country where shingles are any where near common. I assume fitting sheet steel would be far quicker than shingles as well, even with pneumatic nail guns, the benefit of wooden shingles of course is if you have a good supply of timber and a sawmill you can make your own I suppose, they still do shingle splitting in those lumberjack competitions don't they?
In Australia it's a simple choice these days; steel sheet, gal or colourbond, occasionally steel tiles or interlocking highly formed concrete or terracotta tiles, not the simple slab type tiles we have here in the UK and that's about it.
I was amazed when I got here to the UK at the number of different types of roofing from slate tiles, flat simple terracotta, formed terracotta, concrete tiles, various different steel sheet and corrugated bitumen sheet, bitumen felt simply tacked on over ply or chip board and my new favourite thatching, with all of the various decorative touches. When using the highly formed terracotta or concrete style tiles they hardly fix them down at all, in Oz at least on the East coast they are often both tied down with wire and nailed on each tile whereas over here they seem to nail or tie the occasional tile but the rest just sit via gravity only stopped from sliding off the roof by the battens,
The house I grew up in, in Newcastle, Australia was subjected to such strong buffeting wind that despite the tiles being both tied and nailed you could still hear them rattling (despite the insulatin)in a storm and the ceiling will often be covered in fine terracotta chips from all that tapping together.
About ten years ago not so far from my home town but further up the Hunter river, I think it was Singleton they had a massive Hailstorm, now I mean massive hail and a massive storm, the stones were reported as being the size of oranges, from the newsreel footage I believe they were that big, the sheet steel was shredded and the 5/8-3/4"Terracotta tiles smashed to pieces, they even showed a car with a split through the steel roof!! the car's roof was caved in like it had been attacked with a sledge hammer, a few years after that storm I went to a museum in West Sussex, UK and there was an exhibit showing tile manufacture in the UK since Roman times the tiles themselves were near to unchanged, interesting I thought, the thick ones were about 1/2" thick even the Victorian ones were quite thin, I just can't imagine how they would stand up to the cruelties of the Australian weather.
The UK population will be the first to tell you that the weather here is terrible, but seriously, at least no-one gets killed
by hailstones or flying roof tiles.
Best Regards
Rick
Whatever it is, do it today, Tomorrow may not be an option and regret outlasts fatigue.