Eiger Upgrade and Mule Head Questions

Hi, I have a AAA Eiger with a #6 head, which I think uses the XP-G emitter but has no QTC on it. If I'm using lithium primary cells to power it, how much of a brightness/efficiency/etc. benefit would I gain by going to the new XPG2/QTC models? Would it be noticeable at all?

Also, my "old school" #6 head has a medium optic on it. What is the construction of the mule heads like? Is it sealed away behind a clear lens, just without any reflector/optic between the lens and the emitter? Does it use a diffuser material to create the flood? I don't suppose it would be a naked emitter like the ARC-AAA heads of yore? I've browsed this forum for a bit but haven't found any clear pics of the mule heads.

Thanks!

Here's a thread with a Mule picture...

https://www.candlepowerforums.com/threads/344812

... plano lens, no diffuser.

Yes, a new XP-G2 QTC (#8) will be brighter and more efficient

I think I might wait for a 219 mule or G2 with optic and then pull the trigger. Unfortunately both seem to be out of stock on oveready at the moment. Thanks!