You will almost undoubtedly have much better results with a tape player. You can get decent used tape players for a song, and you might even get paid for taking a used car tape player. One of the main drawbacks with MD's is the digital compression and minimized bandwith. Basically, you will find yourself losing the most at the extremes (lousy highs and no bass) if you use an MD player. I toyed with idea about 5 years ago and found the MD's to be completely unacceptable. I have a couple of female friends who do prefer the newer MD players for jogging since they're lighter and smaller. You will also likely find a better selection of chioces if you choose to buy tapes from your local record store.
MD vs. tape
Realizing that neither of these formats are considered audiophile quality, I'm still interested in a comparison between using a minidisk recorder vs. a cassette tape deck for basic recording purposes. My use would be primarily in the car or for taping FM broadcasts, with an occasional home playback of recorded, borrowed CDs/vinyl. I have no substantial investment in either format, but would be interested in a comparison of buying an MD deck vs. a (probably used) tape deck for these purposes. I assume that both formats will become obsolete within a matter of, say, 5 years. So my expectations are only for a temporary system.