PeterW,
I don't have a broad range of experience with flashlights,
and I find your requirements somewhat contradictory, on the
face of it. For my uses, "best" and "most useful" don't
go together with "brightest" and "most impressive" or with
"2D" form factor. Not that bright and impressive and nicely
large aren't nice things, just that I wouldn't find those
things to be the most useful. Your requirements are
obviously different.
For me. the Arc LS is close to the perfect EDC light. It is
bright, but not so bright that if I wake up in the middle of
the night it's going to blind me at first. It is small and
disappears nicely into a pocket. It has a good long run
time and is one of the more rugged lights out there. The
Arc can certainly take some serious use/abuse. The Arc is
one of those lights that you come to appreciate more and
more. It's excellence unfolds over time to reveal the
great care and balance of the design. Also, Peter Gransee
stands behind his lights like no other company on this
earth. It's like you're part of a club. He listens to
your comments and suggestions; responds promptly and fully
to your questions; and keeps you informed on all sorts of
fronts. If you EDC two or three lights, then that might
change things a bit, but if you, like me, want the most use
for the least bulk then definately the Arc LS is it.
Just my two cents, as it were. But if I understand your
requirements correctly perhaps the SureFire L4 would be best
for you. It certainly sounds like an awesome light, and
despite my shameful early post on the L4, I am quite
convinced that overheating is not an issue, despite the
5 watt LED.
Hope this helped some, and good luck.