Each user will have their preferences in battery type. Most models I've owned used AA Batteries.
Iprefer the Lithium Ion. Why? For one thing, it's much easier for me to handle. Instead of multiple batteries to load,you have one battery to load, that only fits in the charger or camera one way. With AA's, I had to fumble with multiple batteries, worrying about making sure I didn't have the polarity reversed (when inserting them into the charger, or the camera).
Also, I've found the Lithium Ion to be much better about holding it's charge when my camera is "sitting on the shelf". With AA's, I'd always need to make sure they had a fresh charge before using the camera.
With Sony products using their "InfoLithium" batteries, you also have the advantage of afar
more accurate representation of battery life remaining. It's my understanding that they embed a processor in the battery itself to help estimate remaining minutes (although I don't know this for sure). IMO, it's the best battery system around.
Mostother cameras (not using the Sony InfoLithium system), only give you a "full battery" icon. Then, when the battery is almost depleted, it's starts to drop rapidly (often with very little warning). This is true for models using Lithium Ion, too (battery remaining indicator is not very accurate).
However, the Sony InfoLithium batteries are more expensive than most.
With my Konica KD-510z (Minolta G500), I can find genericLithium Ion batteriesfor about $10.00 each.
If the P100 is like a P10 I bought and returned last year, the battery charges "in camera", with the chargerperforming "double duty" as an A/C adapter.Some like this.
Personally,I would never let battery type influence my decision in purchasing a new digicam. There are far more important considerations.
BTW, Steve has info on AA Chargers and batteries here (you'll want good, high capacity NiMH AA's, for a model using them). Maha chargers and batteries are very good: