Re: 5w \"S\" vs. \"T\" Vf bin
it equates to more efficiency, and therfore less heat. Since the total power consumed can be drived by multiplying voltage drop by current (from V=IR)
LED that has a lower forward voltage at the same rated current will have less resistance to the current flow. therefore you'll get more Lumens/Watt,...more light per unit of power consumed. It also means the LED will operate at lower voltages when the battery is almost dead.
I'm not sure about battery life. Since it's rated for current * time....mAh... so technically if your batteries have enough voltage to push through 350ma just barely, with lower Vf, they will overdrive the LED unless regulated.
i would say that if the circuit is constant current regulated, then it does increase battery life because the voltage dropoff will be slower. but if it's direct drive it wont impact battery life much cause the LED will make up in a higher current draw and therefore faster battery voltage dropoff. effectively offsetting what the it saves in lower a Vf with more brightness at full battery charge, if that makes sense.
or maybe i'm talking out of my ***.
