Different lights using different batteries. I don't own the D10 (as I tend to stock lots of 123 batts) but the EX10 is a nice light. I also own the Extreme. The Extreme has a clip, but is larger and slightly more difficult to EDC. If you don't already have lights that utilize the CR123, I would go with the D10. If you are thinking rechargables, be careful. My Extreme would not allow AW protected cells to fit in the tube. Most others say they fit theirs, however.