It is possible that they are both true on the different planets. Remember, Roshar has much harsher weather and terrain, but also no need for supply lines, so can retreat faster as well. Not to mention shards.
Scadrial on the other hand, has no soulcaster or shardbearers, and didn't seem to militarize allomancers much in era 1, and also has genteler terrain and weather conditions (an ashfall is much nicer than a highstorm) and so the dynamic could be very different on different worlds.