I was a huge supporter of minidisc in its day, but when your last MD player finally bites the dust and you find there's no replacement available, you'd better have a backup on some other medium! A second hand MD player off eBay is all very well, but it will be used and still have a limited life.

"definitely better than mp3"
Standard MD is 292k bits/second, LP mode is 132k, LP4 is 66k.
MP3 has standard rates including 64k, 128k, 160k, 192k, 156k and 320k
If you compare the two at similar rates, you'll find less difference. The basic compression method is the same, though not identical.

If I ever get around to digitizing or copying my recorded music collection, it will be to hard disk. When storage technology changes (from IDE to SATA, or from HD to SSD) I'll get a new drive and copy it all.