I own both this light and the diffuser. I've tried the diffuser and just don't care for it. I might use it if I used two of these lights, however -- one with and one without. But certainly, it's a personal preference.

That said, any time somebody asks me about bike lights, I now point them at this $23 light. I suggest this, two of the $5 DX PBSF clones, and one of those $1.55 DX flashlight bike mounts and a $2 9 LED 3xAAA flashlight (or whatever they have lying around) as a spare second light and $1 for a pack of AAA alkalines for that. $38 total spent, and they have redundancy and more light than 90% of the bikes on the road.

I used to go the 18650 flashlight approach, but this light is just too good and to cheap to overlook.