JDP, to have 30% battery on a Pearl at the end of the day is common, not bad at all, for moderate to minimum use.

Have you searched the boards here for this issue, as there has been lots of discussion on it in the past year. Likewise, the 8703 and 8100 are different batteries will render usage differently, so they will be hard to compare, in my opinion.

What do you have running in the background on the 8100 (click alt-escape)?