[OneMalt]

For a current production MDR portable, I'd say the Sony MZR-909 from a feature stand point.

For a classic that's built like a tank and performs like a champ, you can't go wrong with an MZ-R50 (arguably the finest MD portable ever built).

 

[Odin]

I'd recommend the Sharp MD-ST880, it's a player not a recorder though, but it's packed with Dolby surround virtualizer. I heard the sound of it and it actually sounds "surround" and full. I haven't heard of the other players so I can't really commment on that. The Sharp has pretty good sound I personally think.

 

[chadbang]

Given my experiences with the older Sony R900 (completely favourable), and the addition of Atrac Type-R and manual recording levels to the new Sony R909 player - I would recommned the 909 as the dream unit at the moment. (I'm dreaming about it, anyway).

 

[Braver]

well, replaced my sr50 with a mt80. I seem to have lost the line out (if it was really there on the sr50, can still put the volume at 30 to get a similar effect with the mt80, according to th manual), gained a lot of shock resistance and quite some battery life. it was also 20$ cheaper since the mt80 is on sale almost everywhere around here. you can spend 50$ more and get a remote, a rechargeable battery and an optical cable...but if you only want a remote, 50$ is a bit much. rather do without a remote and buy more music

 

[purk]

Though, I am just enter the world of good headphones, but I am all md since 1998. To me the best portable MD would be Sharp MD-SS323. This is a 1999 japanese domestic model.
The unit features 13 DSP settings with 2 user define modes. This little guy has blacklit LCD on the unit which is very bright and cool. The sound quality is the best one I've owned. The bass is excellence but not over powered like those of X-bass. The high is crisp and clear.

 

[bearwise]

I have both the R900 and the R909, both are great machines, but I really prefer the R909. In my hands its much easier to use (I've always had trouble with those fiddly little jog-lever deals on the 900.) I really don't know if having ATRAC-R is anything but a marketing ploy or hardware standardization, I have a MDC-D5C deck and have tried ABing recordings made with type R and 4.5 and any differences are really subtle. The only recording I do is the occasional lecture, but have been told that the top of the line Sharps are superior for live recordings.