Definitely Toad. MP3 is not as good as mini-disc, and neither of them are as good as a CD. It's all about file compression; this does make it easy if you are talking about portable players though.
I have Sony's top of the range NetMD player (MZ-N1, I think). I can download MP3s and put them directly onto a minidisc through a USB cable. It also plays WMAs I think, but I primarily use MP3s. With 4 levels of compression, you can go for capacity or quality.
For my dance tracks I tend to compress the files a little, so I have a continuous noise while I jog. But when in the car, I go for 100% quality (for an MP3, that is). I have a mate who mixes dance music, and he's always sending me mini-discs with his new stuff on (not MP3). The MZ-N1 comes in very useful - kind of like having the best of MP3 and Mini-disc.