Hi there,
The answer is the iPod, hands down, if you're majoring on music - it simply sounds the best of any player out there (as long as you chuck the headphones, which are dreadful, and buy some replacement buds/phones).
The Creatives are typically a close second, but are PC only (if that matters to you) and the software/controls are nowhere near as usable as the Apple gear. Great discounts to be had, however, and look out for the models with replaceable batteries - great for carrying spares for long journies, and for potentially extending the life of the unit.
If you're into watching video, too, check out the larger-screened Creative and Archos players as well - make the iPod screen look puny (though it is a superb-looking screen).
We've got a test of video portables - including all those mentioned - in our next issue, out 26 July.