The L4 is great for INSIDE uses where a wide flood beam is needed. It also works well outside (a) for short-range lighting needs, (b) where there's no competing ambient light from streetlights, etc., or (c) when there's no fog, rain, or wet air to diffuse/bounce-back its floody beam.
The E2L (or KL1 on an E2) has a tighter, more focused "throw" beam that's very good for an LED. So, it's a better OUTSIDE light, especially where there is some degree of competing/ambient light. It does lack flood/spill for short-range lighting, but I find it more versatile for EDC and back-up (to a bigger light) purposes. You can use it INSIDE to light up a room via the "ceiling-bounce" method. The E2L also has more than TWICE the L4's runtime.
Both are great little lighting tools with excellent regulation. It all depends on what you want the tool to do.