User blog comment:Rrr2015/BEST HEALING NEN/@comment-5780397-20151109204139

Doctor Blythe is versatile, but while it takes it almost nothing to heal a fracture, closing wounds eem to be a much more time-consuming operation.

Nen Stitches depends on the user's speed, so it too might be unusable in battle; however, if we assume the user is seen, they can just flee while carrying out the operation, and hide, bìthings made impossible by Doctor Blythe. Nesides, if reattaching an arm takes a few seconds, stitching wounds could be much faster. However, as Alex pointed out, it is ineffective against blunt trauma.

From what we know, Holy Chain works only on the user. Since it speeds up one's regenerative abilities, it is safe to assume it works both with wounds ant fractures, and probably with inner damage to some extent, too.

It depends not only on what you what to accomplish, but on whi is using the ability as well: someone lacking Pitou's aura might be even slower when using Doctor Blythe; Nen Stitches could be effective in battle only due to Machi's speed; and Kurapika's chain basically leaves your allies to die.