The Zune concentrates on being a Portable Media Player. Not a web browser. Not a game machine. Maybe in the future it'll do even better in those areas, but for now it's a fantastic way to organize and listen to your music and videos, and is without peer in that regard. The iPod's strengths are its web browsing and apps. If those sound more compelling, perhaps it is your best choice.
Apple now has Rhapsody as an app, which is a great start, but it is currently hampered by the inability to store locally on your iPod, and has a dismal 64kbps bit rate. If this changes, then it will somewhat negate this advantage for the Zune, but the 10 songs per month will still be a big plus in Zune Pass' favor.
If you're still on the fence: grab your favorite earphones, head down to a Best Buy and ask to plug them into a Zune then an iPod and see which one sounds better to you, and which interface makes you smile more. Then you'll know which is right for you.