The L2 is just LED, it has one LED in it that can be selected between basically a high and low. The A2 has a regular bulb in it as well as 3 smaller LEDS. The L2 is really designed to be used on the low setting with having the ability to switch to a high, the A2 is like a regular surefire designed more to be used most of the time with the high on, but has the option of a low which is usefull for reading or if the batteries arn't powerfull enough to run the Bulb, the LEDs will still work for a while after. Some people also prefer having a regular bulb light instead of just LED since it casts more of a natural bright light. There is just something I like about being able to switch between LED and bulb, instead of only having one or the other. However, most do not want to have to deal with a burnt out bulb, so an all LED light is best for them. One thing that I really like about the A2 is the bulb acts as a spot while the LEDs act more as a flood, so you have a very wide light that still has reach, it is great for hiking since you can see right in front of you and way up the trail at the same time. Anyway, The choice really is a matter of personal opinion based on what you think you would appriciate more. (After all, when you spend that much on a flashlight you want it to work exactly the way you need/want it to)

By the way, Surefire has a new light coming out called the U2, that will retail for about $270. This is all I could find on it:

"Surefire is coming out with a new LED model named the U2. A 5watt, single Luxeon with 6 different user selectable modes of operation."

"Yes, we a aware of the need for a variable power 5 watt LED light, and that's why we have built the SureFire Ultra. The Ultra is a 2x SF123 cell flashlight with a 5 watt Luxeon Star and a 6 position hall effect power control ring. The power level is adjustable over 100:1 range, giving 5 watts at the top end and 50 mW at the bottom. Although this light is not available yet we did show prototypes at this year's SHOT show. The production light about the same size as out M3. I'm finalizing the electronics currently."

So, it is basically an L2, but more selectable meaning you will be able to get a longer runtime by setting the flashlight at the exact level you need it to be.