iPod advantages:
+thinner (easier to slip into your pocket)
+a bit easier to use
Zen Vision M advantages:
+FM tuner
+voice recorder
+twice the battery life for video
+supports more codecs (don't have to convert all your videos)
+more comfortable to hold
+better sound quality and 5-band custom EQ
+much more colorful screen
+less scratch-prone
As you can see, the Vision M destroys the iPod in nearly every category. The only reason to buy an iPod over a Zen Vision M is if you absolutely love the iPod's controls/software/other personal preferences.
Where have you heard that a lot of people like the iPod 5g more than the Vision M? I'm pretty sure most people who know what a Vision M is like it more than the iPod (except fanboys).
I am still tryin to decide which to get- Crative Zen Vision:M or Apple ipod 30GB. A lot of people like the apple iPod Video better than Creative Zen Vision: M but I heard that Creative Zen Vision: has better features, battery life and feels goon in the hand and slips right into the pocket pefectly.

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