For MP3 players (if you're getting it mainly to listen to music, which you should be, hah), Sony is definitely the way to go. They are practically famous alone for having the overall best sound in their players, by far. I'm actually about to get a new MP3 player, myself, and I'll be getting a Sony, because the other brands I've had don't compare by a long shot.
The one I had was about the size of a silver dollar and was only 1GB, but the sound was unspeakably better than my Phillips or Sansa, and a million times better than my Zune or any iPod I've ever used; I also loved the overall quality of it, and it was very cute and stylish.
I also had a close friend who had several Sony's and was extremely pleased with every one. Plus, they almost always get the most amazing reviews on electronic websites and such. I'm sure this series is just as good--at least, that's what I've heard (I was actually reading up on these exact players a few days ago~ :O). It's definitely worth the extra money, in my opinion. And you could always find a cheaper model, if you must...
I haven't heard much good or bad about Samsung, so I won't input there, but... I'd advise against the Touch, for sure. It's still very hyped, but nearly every person I've heard talk about the Touch was kinda disappointed by it. Also, it's not made specifically for music, so don't expect that. In my opinion, the Touch is way too much for something that isn't nearly as good as they make it out to be. :\