The XPG2 is a better choice than the XRE in most applications.
A lot comes down to if the throw is for its own sake, just wanting to put a spot of light on a distant target to see if you CAN...or...if you need to SEE something off in the distance.
The asphericals, mostly, are about the former, a spot to see how far it goes...with exceptions for long range shooting, as its a way to get your cross hairs to contrast with your coyote, etc....but you'd use something else first, to FIND the coyote, and so forth. They are also a way to stretch the light when you have a small form factor, and need maximum range, and can sacrifice the size of the area you can see at a time. The XRE is well matched to this function, as the small effective surface area yields very good collimation.
The limiting factor for the asphericals using small but dim LEDs, is that as things get further away, they are harder to see, as they are becoming a progressively smaller proportion of your field of view. This is sometimes known as the railroad track effect.
If you are on RR tracks, looking don them, the tracks seem to converge at some point off in the distance....your eye sees the two rails as getting closer and closer together further and further away. The distance between the rails is of course several feet at every point, but, far enough away, your eyes can't resolve two objects from each other...and, analogously, a small spot of light is eventually too small to see....even if its the same lux as a closer spot, etc. This is why you can see the lights of NYC from space at night, but not an equally lit up but smaller city.
Add in that the effective brightness of the target (Lux) drops off with distance according to the inverse square law (The light is 1/4 the brightness at double the distance...), and a concentrated spot with low lumens will create less lux on target than if it sent the same concentrated beam with more lumens....IE: the more lumens hit something, the more lux result.
Add to that that you not only might want to see the dot of light hit something...you might want to see what its hitting....and the use of a larger, higher lumen LED instead of the XRE starts to become a clear path.
The challenge of course is to GET a larger LED to be able to concentrate the lumens as well as a smaller LED can...and the end product is typically NOT concentrating the beam as much, but say making the beam wider, but, compensating by making the overall beam so much brighter that the resulting lux is STILL higher on target....but, the spot on the target is a lot larger.
That uses more power, and that requires a larger light/form factor to handle/collimate it.
So, the XPG2 is closer to the size of the XRE than say the XML's are, and it has much better lumen output...hence its popularity for a throw based light....essentially a lot more lumens from a still small effective surface area.
With the right setup, an XML2 can be used to get the same beam range with a larger beam spot, but with form factor compromises.
Getting more throw out of a larger, higher lumen LED is harder...but getting the spot to be large enough to see anything is easier.
Using some of the newer techniques, some of the larger LEDs are being used o throw beams further than the old XRE could dream about.
So, if you were about to consider using an LED for throw in a project, I'd consider the XPG2 instead of the XRE.