The difference between the two batteries didn't jump out at me there - thanks for pointing it out. For strict road riding (I'm not a MTB'er), would the NiMH battery really make that much of a difference? I'm not worried about theft/abuse/etc., as my bike is either in my garage, on the train with me, or in a secure locker in my building (i.e., no free-standing bike racks for me), and my riding would consist of a consistent commute on even roads to/from the train and then some 20 mile rides on controlled bike/walking trails in the late evening once or twice a week (hopefully).

Having multiple mounts for different bikes isn't a consideration for me. It'll be mounted to just one bike. The NiteRider NiteOwl that I was borrowing from my buddy did have kind of a different mount, but it's by no means whatsoever a breaking point for me. I just want maximum illumination for the $$. The mount of his NiteRider was functional though, and so I really have no complaints with it.

I guess from my low-budget perspective, I could put out the extra $30 for the TrailRat, or I could just get two RoadRats - one for the handlebars and one for my helmet (which I'd kind of prefer anyway). If the lead acid battery really is that bad though, I suppose that even with a limited budget, I should put out the extra cash anyway?