I'm on my second Creative product, Zen Vision:M. I had a Zen Micro for about 8 months. I'll only mention the current fight for top mp3 player since I have the most experience with it.
Pros - one of the big things I like about iPods is iTunes. Being that this is what you will be using to transfer your media it helps that it is excellent. Another benefit is content. Just about any kind of content is available for iPods. Lastly, you can find any accessory you could possibley want for an iPod. Also it helps that iPods are widely available in stores.
Cons - limited formats. You can only use mp3 and Apple propritary formats on your iPod making it impossible to upgrade to a device other than an iPod with little to no effort, although there are programs to convert but its a hassle to convert 1000+ songs into another format unless you use mp3. Although the video iPod has a very good display it only supports 65k colors. Its only a con when comparing the 2.
Pros - support for multiple formats. I prefer WMA over mp3 so this helped me make my decisions. This also helps if you want to use a subscription service since they use DRM WMA usually. Another big thing I love about the Vision:M is Drag-n-Drop capability in XP. This is a great time saver in terms of transfer. The Vision:M also supports a number of video formats so more than likely it will play. And if it won't it comes with software to convert it for you. The display is the first thing that wow'd me when I got my Vision:M. It supports 256k colors. And you can really tell.
Cons - Creative software. It has a separate program to do just about everyhting you want it to do. I hate this but you gotta deal with it. Not many accessories out there currently but more are popping up here and there. It would also help if it was widely available in stores.
I give them a tie when it comes to manueverability. The click wheel is great but so is the scroll pad. Different strokes for different folks.
Verdict - I take creative in this battle. I've used both products and both are really good.
P.S. If anyone mentions a "cool" factor of the iPod slap them for me. That has got to be one of the dumbest reasons to buy anything but it works somehow.
I'm about to get another mp3 player and I'm not sure if I want an ipod or another less common mp3 player, All recommendations and reviews welcome. Pros and cons please.