I'm guessing it's probably mostly an issue of rating systems. It's kind of seeming like SF are becoming slightly less wildly conservative in their lumen ratings. Take the E2DL and LX2 for example - it seems that the LX2 is generally brighter than the E2DL, but not by 80 lumens. My guess is that SF's output measurement techniques have been updated in some fashion, and so new models are being given more realistic ratings as they're released. If that's the case, one might wonder why their other models haven't been updated to their new rating system, but they probably have their reasons (consistency in military contracts and accounting for older releases already purchased that wouldn't meet the updated ratings, etc. seem like reasonable possibilities).
Or maybe it really is just an issue of the M300A being a more recent bin XR-E (though I wouldn't think that would account for a 30 lumen difference...).
Of course, I don't have an E1B and M300A to compare side by side, so maybe there really is a 30 lumen difference between the two? Or the runtimes are measured differently?
