Submitted by Leo
I think that for military use the Petzl Tactikka XP Adapt is more useful because you have 4 color-filters/diffusers of witch you can always carry two, one in the light and one in a special holder on the elastic band. In addition, you can also click it to your molle vest or helmet. Last but not least you have a boost button to give you instant maximum lighting ideal for looking at something far away.
ED - Leo, I'd considered the Tactikka XP (REI didn't have the XP Adapt) before selecting the Plus. While the XP and the Adapt do have some nifty features, I thought both were more light than I was looking for.
For me, what I wanted was some thing small, light, durable, and capable of both red light and white light. While the XP has a spotlight capability as well as a "maximum output" mode, I've already got the spotlight function covered with the GI-issue Surefire Millennium flashlight mounted on my M4. Moreover, while the 4 color capability of the XP and Adept are nice, but nine times out of ten all I ever use is red light, and if I need to use a different color for something, then I'll brake out a box of chemlights (not to mention that, while you can change colors on the XP light, there's no place to store the additional filters, other than in your pocket or someplace similar, which for me, is just more parts to lose in the dark.)
Bottom line, I can't fault the XP Adept, it is a good light, and like I said, I did consider it, but at the time it was more money than I wanted to spend on more light that I didn't need.