For the most part, it'll be nominally brighter (5-10%), and a lot longer runtime... I'm guesstimating a little under 25 hours high brightness (non-moon) with a Li-AA. I never really timed mine, but it's still running off of a Li-AA since November of last year, and I haven't changed the battery yet (I use it about 5-10min a day, although it is getting on the dim side)...