but I’ve grappled with the same dilemma for the last 2 seasons. Stationary warmth vs moving warmth. This is my solution.
I have given up fleeces in favor of 2 synthetic insulation layers (Montbell UL Thermawrap vest + MEC Northern Lite Smock). I wear both layers when stationary for the equivalent warmth of 1 heavier insulated synthetic layer but when I’m moving, the heavier MEC smock gets strapped to the top of my pack and I only wear the vest + my windshirt. When it gets (or I get) slightly colder, I ditch the windshirt/vest combo for the smock and I can play with all the combos in-between.
Its a very versatile system. Three pieces = lots of combinations for any occasion.