What buckpuck should I use with a 12 volt 5 amp/hour SLA battery with a Cree MC-E LED?

First:  The Cree MC-E LED is rated at 350 milliamps but has a max voltage of 700 milliamps.  Does that mean I should get a 350 or 700 milliamp driver.  

Two:  On ledsupply there are wired buckpucks with external dimming and potentiometers.  What is the difference between external dimming and what a potentiometer would do (lower the voltage and so dim the light)?

Three:  On Deal Extreme it says driving voltage/current is 3.2V~3.5V, 350mA~700mA.  On ledsupply it says "12.8Vf - Typ. Forward Voltage @ 350mA and 13.6Vf - Typ. Forward Voltage @ 700mA?  What is the difference between driving and forward voltage/current?  What voltage and current comes out of the buckpuck?

I am trying to make a bike light.  Thanks for the input


Use a lower current than the maximum - on full whack these things get hot.

A dimmable one  saves batteries.

The MC-E is FOUR leds in one package, they are wired in series, so you get roughly 12V of forward drop over the whole device (4 x 3.4V)