Some corporate notebooks such as the Dell Latitude line include both. This one falls squarely under the category of things you can never get enough of. But there are a few general rules to keep in mind. Pound for pound, a Li-Ion battery delivers more power and is therefore more expensive. Second, in general the bigger the notebook, the more battery life you'll get.
Larger notebooks have bigger batteries, measured by the number of cells.
Still battery life varies quite a bit, even among notebooks that are in the same class. The only foolproof way to compare battery life is through performance tests such as the ones used in ZDNet's product reviews. We know, that translucent case, bright colors with names like blueberry and tangerine, and soft, rounded edges are all mighty tempting. Looks do count for something, but there's more to a notebook than just a pretty face. When choosing a notebook PC, you need to think long and hard about the pros and cons of each platform.