Blackbar is a narrow tool: it finds secrets in a screenshot and burns them into the bitmap. Most of the software people already use for this is broader and better at everything else. These pages say plainly what each alternative does better, cite the vendor's own documentation rather than rumour, and stick to the one argument that is actually about technique — drawing over pixels and destroying pixels are different operations.
Apple documents a Redaction Selection tool for PDFs and no redaction tool for images. What that means when you black out a hostname in a PNG, where the PDF detour goes wrong, and the five jobs Preview still does better.
TechSmith itself warns that blur and pixelation can be reversed and recommends solid shapes. Snagit's Smart Redact detection list next to Blackbar's 27 detectors — one is PII-shaped, the other is credential-shaped.
CleanShot X documents solid redaction, so the technique argument does not apply. The real differences are automatic detection, an editable project format versus a one-way burn, and whether the binary can reach the network at all.