:) Here's my rundown of my experience with a few different battery types in sabers:
Duracell standard coppertops- Typical LR6 1.5v Alkalines. Good in a pinch if you are completely broke. I don't recommend them for any long periods of time. They drain quickly and produce less than stellar results with light and sound.
Energizer standrd and MAX- Same as duracell standards... Crap out VERY quckly.
Everready "Cat 9"- Used to be a state of the art battery in the Late 70's. Pretty Much worthless in a saber. In stock FX, they cause intermittent "dark spots". Lifespan is not too shabby if you actully find a good set. AVOID!
Panasonic, Rayovac, etc- A tiny upgrade to the Cat 9's. Stay far, far away from these. Utter garbage in luminosity and sound.
Energizer e2 Titanium- Great luminosity and sound in a Stock FX (6 cell especially). Mid-range lifespan...MUCH better than standard Energizers (Max). Decent pricing for quality.
Energizer e2 Lithium- This is THE battery to use in a Lux converted FX Hands down. Great boost in sound, and Luminosity is BRIGHT! More expensive than any other AA I have EVER used, but well worh it. If you use the saber they're in a lot, the life can be a little short however.
Duracell Ultra Digital- These are GREAT for a stock or Lux FX. Especially in terms of battery life. It has been my experience that Ultras last the longest out of any other battery in an FX. They lose a little in Luminosity if used in a LUX, but not enough to detract from performance.
Duracell PowerPix These puppies make your saber VERY Bright, but the run time is really short (especially in a LUXEON). They are very affordable compared to e2 Lithiums, but with the run time they offer, you're better off buying Ultra digitals. Unless of course, you want to impress a crowd with a quick duel! ;D