Had same dilemma just last night. Went with the L4. I actually returned my L1 and exchanged for an L4 (yes, after I touted the L1 so highly in another thread). Since I'd only had the L1 a few days, Sports Ware was good enough to let me upgrade to the L4. I was able to go into their dark, long stock room and try both the L2 and L4. L4 had much warmer white beam, but otherwise I could not distinguish it's throw or overall output from the L2 on high. The L2 is actually over 1.5" longer, and besides, they only had the display model L2, and it's tailcap looked grey compared with the OD of the rest of it's body.
Another consideration was the L2 is not as lego friendly, but I now have the E2E body that comes with the L4. Since I also have a KL1 head, I can use the KL1 head on the E2E body for long runtime, with alot of throw. Or, use my F04 diffuser, and on and on, and on.
So, unless you reeeaalllly need the low setting and it's worth less pocketability and less lego-ability, get the L4.
Later,
Jeff.