Pocket PC has more multitasking support and very good media support (movies, games, music).
Palms don't really multitask, though some devices let you play music and do one more thing at a time. Usually though, they quit one app as soon as you launch another.
People do say the Palm's usual calendar, contacts, etc is easier to use, but Pocket PC's info management works well with Outlook, which is included with Pocket PCs. In both cases, there are 3rd party tools for info management as well.
Some Pocket PCs have a CF slot, which is very helpful too. They can take much cheaper memory cards, cheap CF wireless cards, etc.