Outdoors, definately go with an incan. This is not to say that some LEDs can't match an incan in terms of throw or beam configuration, but when I am outdoors, I prefer incan because of the colour temperature and ease of depth perception. Yes there are LEDs that do provide lovely depth perception etc, but they are harder to come by than an off-the-shelf incan product.
Regarding e2e vs L4:
E2E:the term "hotspot" was made for the e2e in this comparison, the e2e's circular hotspot throws very well and complements the perfect, smooth spillbeam. Most of the light is focussed into the hotspot; the spill is much dimmer (but is still useable).
L4:is no slouch, in fact I would probably say it puts out more light overall than the e2e BUT the beam configuration is so different! The L4, as others have said, puts out a larger hotspot and not only that but it has a much brigher spillbeam. It's as though the light has been more evenly spread throughout the beam. Also consider the "luxeon lottery" when you're going to be buying a lux! I find that the white luxeons tend to "wash out" under ambient light. This might be a consideration for you.
If you need to use the light a lot I think that it would be worth your while looking at a Stinger, Tigerlight or one of surefire's excellent rechargeable lights. These incans throw well and when you are performing a medium/longer range inspection should serve you well. Add to that the lower ongoing running cost and you have a winner. Given my understanding of your situation, I would definately pick one of these lights as my main light. Even though they are larger than your desired format, they provide sufficient output that most medium-long range treelines should be visible.
I do think that you need to consider a smaller light to keep on your person at all times in case your "main" light fails. I would strongly consider an A2 for this purpose. The 2 levels are extraordinarily handy and have saved me much trouble in the past. I assume that you will be walking, making notes and performing other short-distance tasks. The lower level of the A2 is perfect for these tasks. The led only setting conserves batteries and is, relatively speaking, good at preserving your night vision.
edit: I noticed that you mentioned that you wanted a clip. Could you clarify this? Surefire's clips are not intended to secure a light to a belt: many people have lost their lights this way. The clips are intended to keep a light at the top of one's pocket so that it may be easily accessed. Is there a reason a belt holster would not suit your situation?