I'm comparing the Windsor and the Imperial 2. It looks like the Imperial 2 has twice the battery storage and 20 vs 12 LED lights, and it can put out 350 vs 150 lumens. (Correct me if I'm wrong! Are the LED lights in the two lamps different? 20/12 |= 350/150.) Are the solar cells in the Imperial 2 larger? I would think this is the limiting factor for lighting in the winter. If not you'll eventually have a battery insufficiently charged to run the lights for long winter evenings after overcast days.