I noticed recently that I had edited a posting of an otherwise informed answer solely to replace "q-bit" with "qubit", but then I note that I don't bother to correct the unhyphenated "qbit" to "qubit" when I see it in other similar questions and answers.
Should we have a preferred policy to encourage use of "qubit" in much the same way that we lightly encourage "quantum advantage" or "quantum computational supremacy" over "quantum supremacy"?
Nonetheless there appears to be less than 100 postings that use qbit, while the vast majority, >4k, use qubit, so it might be a don't care in the grand scheme of things. Most of the high-rep users on this site use "qubit" I believe, so I'll go out on a limb and say that "qubit" is preferred but no one will make a stink about "qbit". Maybe some monstrosities like "Q bit" or "quibit" would trigger an edit.