B is found on most consumer decks and C on some consumer decks. C is slightly better. Both essentially encode your signals to reduce tape noise and are then decoded on playback. HX Pro attempts to do this without requiring a decoder on the other end and is a good choice for tapes you hand out. If you are using a 4 track multitrack and you have a B-C option, try using C. Better is dbx for this which is not often found on consumer decks and definitely requires a decoder whereas B and C won't sound so bad (just noisier) without a decoder on playback dbx actually does a lot more to compress and alter what is recorded so the tape when played back without a decoder will sound flat, lifeless and probably overall weird.
