Dolby B is much less sensitive to media. It works pretty well on all good quality tapes, and even on cheap ferrite tapes, I never noticed irritating artifacts. Worst thing is a loss of the top octave when decoded, when a cheap tape doesn't "hold" the increased treble from the encoding filter. You can always turn the decoder off, which has the effect of boosting the top octave. Of course, with the decoder off, you won't have noise reduction but instead will have treble boost. The increase it gives to the top octave is usually welcome on those cheap tapes anyway.

This isn't the case with Dolby C or HX in my experience. Some tapes just can't be made to sound good with them. You can't expect a tape encoded with Dolby C to sound good if the decoder is off, so cheap tapes really couldn't be used. When they don't retain the increased HF from encoding, you can't just turn off the decoder so the tape sounds bad either way.