I think soft shells are great for day hikes or skiing– single purpose or short term events where you have a reasonable expectation of the weather. They are great for commuting and they look good too.
I've asked a lot of climbers about soft shells and what I heard is they are great for casual or moderate conditions, but not good for more extreme stuff: if it is really wet, or really cold, the soft shell doesn't meet the demand. As I can buy a really good rain shell and an insulating garment for about the same price and weight as a soft shell, I've chalked them up to being more outdoor fashion than hardcore backcountry gear.
The windshirt excels in a pallet of ultralight clothing as you can use it for multiple layering techniques and retain the light weight and low bulk. Soft shells are heavy and bulky for a single garment, and they aren't cheap.
I have a Marmot DriClime Windshirt that is a good example. I really like the garment a lot, but the insulation is tied to the shell, so I am always committed to the full 16oz it weighs. I have a Montane Lightspeed that is about 6oz and I can layer that with anything I like and get a hood too. It takes up the space of a small apple. Layering it with, say, a Powerstretch long sleeve tee gives me about the same insulation as the Marmot, yet I can wear the Powerstretch alone, or the shell with a silkweight tee, polyfill vest, or all the above. Breatability and DWR are neear identical. If you want to get your wardrobe light, it must have that kind of flexibility.