Between those two, the Scout.
But the best answer is "Neither - Light Monkey 3W LED Backup Light." On my single tank rig, I have one HP LED version Scout and one LM 3W light (for my doubles rig, it's a pair of Gulftex Photon Torpedos, which I like better than either the Scout or the LM because they're stubbier). As compared to the Scout, the LM is $35 cheaper, has better grip texturing on the body, a double o-ring seal vs. the Scout's single o-ring seal, and a significantly tighter beam. Both are around the same brightness, with the Scout having a slightly whiter/bluer light than the slightly yellower LM 3W LED... still, while I like the Scout's color, I think the beam tightness is more important. Interestingly, the Scout claims 4 hours run time on 3C batteries, while the LM 3W claims 10 hours on 3C batteries. No idea what the real deal is, as I swap batteries out pretty religiously. LM customer service is also going to be better than Halcyon; LM is smaller and extremely responsive. The experience is like dealing with Atomic or Shearwater.