..... I'm also curious about the Preon II compared to the Fenix LD05, which I haven't read about yet.....
My favorite form factor for EDC is a 2xAAA light. I have a Fenix LD05, Streamlight Stylus Pro, and Inova Bolt, and am impressed by the first two lights.
The LD05 is longer and heavier, but built very solid due in part to the stainless steel bezel. The pocket clip is firm and does its job well.
There is no knurling so the LD05 can be a little slippery. The switch action feels substantial and accidental activation seems unlikely.
The light emitted has a good tint and is free of annoying artifacts.
The LD05's high level throws farther than I expected -- about as far as the Leatherman Serac S3 (1xCR123A). Though I don't use the highest level for long periods, the LD05 has never become hot.
Some owners have reported that they can see flickering at low levels due to a low PWM frequency, but my eyes cannot detect it unless I move the flashlight around rapidly back and forth while staring directly into the beam -- an action with little to no practical use.