Some soft shell jackets have a polyester pile or fleece finish on the inside for extra warmth and comfort. Others don’t have this, so they won’t be as warm. However, you can of course wear them over other, thinner, insulating layers, such as a fleece or thick base layer. If you want a soft shell just for colder conditions, then an insulated one is ideal. If you want a year-round soft shell, then a less well insulated design that can be worn over other insulation will be the ideal solution.