I've just bought the niterider minewtx2 (not the dual) after having a similar dilemma with pretty much the same names cropping up. In the end I went on a bit of a whim and the fact it scored highest in Top Velo's 2007 light review (I've bought from Top Velo's recommendations before and never been disappointed). They reckoned on about 6hours on the low setting, I've only had it on for about 3 hours total so I can't confirm that (but as I say, I trust Top Velo).
FWIW, tonight was my first fully dark commute (similar in nature to davep's) with the new light and I was pretty amazed at the amount of light it was throwing out, I certainly didn't feel like I needed a second light, it was pretty much like having a car headlight attached to the bike (and that was on the low setting as opposed to the full beam). My only criticism was that my Shimano gear cables cut across the beam casting a bit of a shadow! It's a nice looking bit of kit with a warning to let you know when you're down to the last 15 minutes of charge too.
TBH, the conclusion I came to was that for about £150 you are going to get a good light, it's just up to you to decide which one suits your riding best.