No difference outside, just the torx screw on the clutch (force 1, 1x11):
Sram says it provides a "smoother torque curve for a quieter, more consistent operation and feel".
From Mountain Biking Australia:
http://www.mtbiking.com.au/gear/sram-eagleWith the first generation Type 2 derailleurs, the clutch was often excessively tight and developed a knock that could be felt through the bike. It was then replaced by Type 2.1; a non-serviceable rendition that didnâ€™t suffer the tightness issues but often lacked clutch forceâ€”more chain slap was usually the result. So far the new Type 3 clutch seems to have these issues sorted. The Eagle derailleur has a nice tight spring and enough clutch force to keep the chain firmly in place. When the cage does move, the action is smooth and thereâ€™s no feedback through the frame. The Type 3 clutch isnâ€™t exclusive to the top-dollar Eagle parts either; it also features on the recently released NX derailleur and over time it will be phased in right through the SRAM range.