Explain your answer; would the difference be in output, beam profile, what?
Also, what would be the difference between a typical Q5 XR-E drop-in and this emitter…
S2
I thought that the Q5 and R2 are simply bin numbers and denote lumen output with R2 being one step brighter. I think XR-E Q5 or R2 have been shown to be a little brighter than XPG Q5 or R2 but with XPG going up all the way up to the rare S-2. (Q,R then S ) I know both the XR-E Q5 and R2 can be driven very hard to make a great thrower. I don’t know if the XPG can be driven as hard as the XR-E or not. Although I would have to guess that the S-2 wouldn’t be bad. I have one light with the XPG-R5 and it throws Ok. But not like the XR-E Q5.
I hope I have completely confused you with this gobbledigook and I can absolutely guarantee that it’s at least 25% accurate. 
ps. when it comes to that drop in you can drive it much harder than what that driver can.
I was thinking lumen output, but I saw the link I provided and wondered if it makes that much difference. I never cared for the XPGs.
You linked to an xpe ...not an xpg or a xre
It's got a nice driver and i like wc tints they are usually pretty decent tints .......xpe has pretty good throw too
driver -
It says XPE R2 so I was curious as to what kind of beam I would be getting and whether it was like or unlike the usual R2 beam.