i have a fenix l2D – i think, it's the 2xAA one that everyone seems to have.
it's got a 110 lumen mode, and a 180 'turbo' mode.
i use it as a zip-tied-on helmet-mounted spotlight, with a 900 lumen LUU on the handlebars.
i find i 'see' more when i turn my headtorch DOWN to 110 lumens.
my eyesight isn't great at night, and i find i rely on shadows cast by my bar-mounted LUU to judge distance/durface detail.
(anything that sticks up like a root or a rock will cast a shadow). if i run my fenix on 'turbo' – these shadows get filled in with light, and i can't see the roots and rocks anymore (cos the shadow has gone).
i'm very happy with my fenix l2d – it's very well made, and lasts way more than 2 hours on 'turbo' – i've never managed to run it down on '110' mode…
(using sanyo 2700 mAh batteries)