I always go with light insulation on both pants and jacket. Even with hiking, opening the vents and unzipping the jacket will cool me off enough to the point where I am comfortable. I used to have shell pants and it was one of the worst choices I have ever made for outerwear. THey make layering a bitch, where with light insulation, you can be toasty to moderately warm in a huge variety of temperatures. I have essentially worn the same layering setup for the whole season +- a shirt or two and I have been fine (east coast) and this winter has had cold as fuck days and rainy days.
IMO always go light insulation pants, and I like light insulation jacket, but usually a shell jacket will work better. Its easier to layer up and down with a shell jacket, not so much with pants.