Claudio is virtous while Borachio is villanous. For example, in 2.1. 301-303, Claudio shows his gallantry when he says, "...Lady as / you are mine, I am yours. I give away myself for you / and dote upon the exchange." In contrast, Borachio is underhanded and far from gallant. As evidence, consider the lines in which he plots his deceit of the innocent Hero (2.2.41-45):
will so fashion the matter that Hero shall be
absent,--and there shall appear such seeming truth
of Hero's disloyalty that jealousy shall be called
assurance and all the preparation overthrown."
As for Hero, she is somewhat like Borachio in that she attempts to use deceit to justify ends, but unlike his, her intentions are without malice. In 3.1.16-23, she tells Ursula and Margaret:
Now, Ursula, when Beatrice doth come,
As we do trace this alley up and down,
Our talk must only be of Benedick.
When I do name him, let it be thy part
To praise him more than ever man did merit: 20
My talk to thee must be how Benedick
Is sick in love with Beatrice. Of this matter
Is little Cupid's crafty arrow made,
For her part, Margaret has a bit in common with Borachio in that she too has connections to the underworld and the lower class in general. Still, unlike him, she has no evil intent and is brought into the web of deceit as a relative innocent.