I never had or handled an original, second, third or whatever gen of the ARC LS. So I don't know about levels or such.
I do have some experience with Fenix, and still very much appreciate my P1. It is a simple LUX III single level 123 light.
But my limited Fenix D experience still says for a reasonably priced modern light the LOD, L1D, L2D, P1D etc. will do nicely.
I can basically go through my day at work, use a 1W 1AA and be perfectly happy. I don't need the brightest 1AAA, 1AA or 123 lights.
You can still grab a black P1 at FenixStore!!!!
Joe, the Arc LS had two basic characteristics. 1) it was a Luxeon light of maybe 15 lumens in its early standard versions or maybe 25 lumens in the $150+ premium versions near the end. This was bleeding edge for that era but totally unimpressive by today's standards, and all the Fenixes, MTE's etc. blow it away in terms of pure lumens. 2) It had a purist (though modular) design philosophy and was built like a tank. Nothing Fenix has ever built comes anywhere close. That is why it is still in high demand by modders today (Groundhog66 just sold a nickel plated one on Custom BST for something like $250). I don't see anyone modding Fenixes with that kind of TLC.
A lot of respondents in this thread (and on CPF in general) totally ignore characteristic #2 of the LS and as such have been recommending the digital Fenixes, which I think leaves out an aspect that's more important to some users than others. I guess Bigred checked out the description and liked what s/he saw and placed an order, so that's fine. The original question was too vague to know which way to answer. The several interpretations to "Arc LS replacement" that I can see are:
1) a rugged, high tech light of coherent, purist design that uses the best available technology and is (like the LS) somewhat insensitive to cost. This would be the Novatac/HDS which go up to 120 lumens, far beyond the original, plus add features like multiple brightness levels and (HDS Tr70) a red led for night vision, while staying in the same price class as the original.
2). A rugged, purist one-level light that puts out 15-25 lumens like the original LS did, using modern leds but otherwise not trying to be bleeding edge. This is the Peak Pacific (HP or UP) which costs a lot less than the LS did, though its performance and features may be considered boring by today's standards.
3) A high tech, low priced light that tries to maximize technical features and lumens while sacrificing ruggedness and design coherence in a quest for "bang for the buck". This is the Fenix, more features than you can shake a magic wand at, while still far less expensive than the LS. However, at least some LS aficionados don't find its design to their liking.