Packing considerations. The Photon is flat, but wide and irregularly shaped, so it doesn't stack so well.
The small LED I have in there is one of the smallest I've seen. Its diameter is about the same as the photons thickness, so depth wise it doesn't take up any more space. It is a little longer, but it's shape allows it packs away neater.
Plus, it's activiation is similar to a surefire. Twist for constant on; and if you twist it so that it's not quite on, you can simply push the tailcap for momentary light. When "locked out" it can't accidently be activated by packing the items too tightly.
The larger LED is white. It has a push button, but it's angled so it won't be activated (I get away with it because it's in the matchbox, and the photon won't fit unless I remove even more matches)