The Special 6 Shirt is cut 2″ longer than the Mountain Shirt. Buffalo say: “This helps with water run off from the shirt and tends to fit taller / broader individuals slightly better than the Mountain Shirt”.
I have two Special 6 shirts- one ripped to shreds, which gets worn multiple times a day in winter for walking the dog and biking, and one for best.
The Active Lite Shirt is for high-effort activities (running etc). I use mine for spring / autumn biking. It has a non-pile lining.
This is where I get confused – The website says the Active Shirt (and the Special 6) both have a Thermopile lining. The outer fabric on the Active looks similar to that on my Active Lite and so must be more breathable (and is possibly less durable).
PS: If you are on Facebook, might be best asking Buffalo direct: https://www.facebook.com/BuffaloSystems