I just discovered the bulb on my Fenix LD10 is not the same as the bulb on the current production of the LD10. Important note, that doesn't necessarily mean my older bulb is inferior. It may be a matter of preference.

The bulb in my LD10 is a Cree XR-E LED Q5. In comparison, the bulb in my LD15 is a Cree XP-G LED R4. (Sorry, I don't have a current LD10 to compare.) The beam in my LD10 is rated at 120 lumens, and my LD15 is rated at 117 lumens. However, my quick non-expert opinion is that my LD10 is approximately 10% brighter than my LD15. The LD10 throws a more natural yellow-ish beam and has a brighter and more defined spotlight. The LD15 throws a whiter and less defined spotlight.

I value a brighter spotlight more than brightness outside the spot light area. However, I have a feeling manufacturers may rate lumens based on the overall brightness of the entire beam. So, I view the lumens rating as being a general guideline at best. I guess it's difficult to get an accurate assessment of a spotlight before you view it in real life (?).