Yes, but I don’t know any of the details about why. I was wondering about this too.

D4 XP-L HI is more throwy than FW3A XP-L HI. It’s roughly 20 kcd vs 12.5 kcd. The D4 has more lumens and more reflector area, and the optic isn’t frosted.

Benefits of 4 emitters in a FW4A:

  • More lumens
  • Potentially more throw

Benefits of 3 emitters in a FW3A:

  • Lower cost
  • Compatibility with popular standard optics and popular standard MCPCBs
  • Smaller head, without the need to make custom optics
  • A proven and widely-loved beam type
  • A bit lower power and less heat (which are both important on such a small light)
  • Slightly better tint in low/med modes

What a lot of people would really like to see, though, is a FW1A with just one emitter:

  • Much more throw
  • Much less heat
  • Lower cost
  • Reflector-style beam
  • Compatible with more types of LEDs
  • Better tint in low/med modes
  • (however, would probably be longer, and turbo might overdrive low-Vf emitters when a high-amp cell is used)

The slightly lower Vf of a 4-led light compared to a 3-led light doesn’t really improve efficiency on this type of driver. It mostly just makes more lumens and more heat. There’s a larger voltage overhead, but this isn’t converted into more light… it just gets burned off. To get a meaningful efficiency boost from extra LEDs, it would need a buck or boost driver.