It depends on your value system, really - virtually everything will have some advantages over something else, but you may or may not consider them advantages.
Some reasons MD are often preferred over an MP3 CD player:
1. MD is smaller than even those 8cm/3" CD-R's;
2. The MD disc is enclosed in a cartridge so you don't have to handle it with so much care;
3. MD allows you to edit its contents, with greater flexibility than CD-RW;
4. ATRAC encoding is often considered as better-sounding than MP3s of similar bitrate;
5. Some CD-R's don't last for more than a few years, MD seems to last much longer than that in general;
6. Manufacturers have often paid more attention to MD portables (over their CD portables), which results in better materials/parts, better user interface and often better sound;
7. Many MP3 CD player makers are inexperienced at portable audio, which means their user interface and features may not be as convenient as the MD portables' ;
8. If you want audible FF/REW within a track, there are many MP3 players that won't let you do it... some CD players also take ages to read the folder tree on a disc, and MD portables typically do that in less than 7 seconds...
Those MP3 CD players also have advantages over MD (e.g. less capacity limit). I struggled for months between MD and two iPods, I think it really comes down to what you want and need out of your walkman.
While I have stuck to MD, I really don't like the way NetMD attempts to protect copyright. It makes me feel like certain Asian immigrants in the US during world war II, needing to argue that I'm "white" so I can avoid discrimination :roll: