Many of the bite patterns used by numerous layout people often result is rough edges of extra remaining material sticking out the side. IF one doesn't need a smooth edge for mechanical fitment, this is not of major concern. But if a smooth edge is needed, then using a V-scored edge for mechanical separation or even milling the edges of the PCB may be necessary. Rat Bites can be economical for hand separating, especially if one uses a pattern that will tend to undercut the edge and not leave estra material protruding outward, provided that you've kept enough pullback and placement keepouts so the "dent" in the edge of the PCB doesn't compromise the integrity of the assembly. I've also found that Rat Bites work better on thinner PCBs - when one has thicker (>.093") PCBs they tend to require alot more holes for easy break, but then the assemblies also tend to become more expensive and candidate for mechanical separation with V-score.