|I need an UNBIAS comment on that, preferably from a person who has an MP3/AAC player and a MD player. Portable of course since I'm thinking of which one I should be getting
I've heard a number of MP3 players, and a number of MD portables. Given good equipment (earphones, even an amp), MD simply sounds better at comparable bitrates (or even lower bitrates than MP3). HOWEVER, that may not matter. If you're going to be using the portable in very active and/or noisy environments, the truth is any difference in sound is going to be negligible. I'm going to assume that sound quality isn't the end-all criteria for your choice.
When comparing MD and MP3 players, more important than absolute sound quality IMO are your needs/intended uses. There are several different kinds of MP3 players: hard drive-based, solid state-based, and CD-based. They each have strengths and weaknesses, and advantages and disadvantages when compared to MD. You can't simply compare "MD vs. MP3."
Do you want absolute sound quality, portability, battery life, low total cost, and the ability to record on the run, and are you willing to bring along a number of discs and swap them out? MD is the way to go.
Do you want to be able to have lots and lots of music (maybe your entire collection) in a fairly small package, and are you willing to give up battery life, risk hard drive failure (low, but there), and pay a little more? A hard drive-based MP3 player is probably better.
Do you want the smallest possible unit with the best anti-shock, and are you willing to give up sound quality, battery life, storage capacity, and low price? Solid state MP3.
Finally, do you want cheap media and good storage capacity, and are you willing to give up shock resistance, small size, and battery life? CD-based MP3.
Figure out what YOU need, then decide on the best solution for YOU.