WM Caribou and Versalite in 6' Left Zip
Side-by-side comparison of my winter and summer WM bags. From this angle you cannot really tell the large difference in loft, but it is considerable. The Versalite achievesto my measurementsa minimum of 6.5" of loft on the center of the lowest baffle tube, not the seam. Naturally, insulation at the foot box and from the torso up is more considerable. Additionally, the continuous baffle design allows the user to unzip the bag and shift down accordingly from top-to-bottom, or vice versa, relative to the temperature. Another photo I posted shows the difference in hood and neck design.
*The Caribou, not currently stocked at backcountry.com, measured a minimum loft height of around 4" of the lowest box baffle.