Between me and my husband we've owned more MP3 players over the years than I can count, including Sansas, iRivers, iPods (classic & touch), the Ibiza Rhapsody, etc. But, the last few years I've settled down to one line of players. Why? Because I was happy to discover how well-designed and fun to use the underappreciated (and widely mocked) Zunes are.
The new Zune browser is surprisingly good, but not as good as the iPod's. It works well, but isn't as fast as Safari, and has a clunkier interface. If you occasionally plan on using the web browser that's not an issue, but if you're planning to browse the web alot from your PMP then the iPod's larger screen and better browser may be important.