The short answer is no, sympathy and benevolence are not the same.  Sympathy
is the faculty for fellow-feeling in Smith.  Another way to put it is that
the faculty of sympathy is how we are able to sense others' approval or
disapproval.  The faculty of sympathy helps moderate our desire to pursue
our own interests exclusively (pure selfishness) because we also desire
others' approval, which we will not get if we are merely selfish.  This,
incidentally, is the basis for Smith's criticism of Bernard Mandeville's
argument in *Fable of the Bees*. Smith's criticism is not about unintended
consequences (where, in Mandeville, vice begets good), but about Mandeville
getting human nature (motivation) wrong.

Benevolence (having others' interests at heart) is a motive with which we
tend to sympathize favorably, naming it a high virtue. The judgment that
benevolence is a virtue comes under the general heading of Smith's treatment
of propriety; we sympathize with actors whose motives are benevolent because
no motive could more admirable.  But propriety also extends to negative
evaluations: we condemn behavior that harms someone, *but* we do so in
Smith's view because we sympathize with the resentment of the person who was
harmed -- that is, we find her resentment fitting in terms of its (the
resentment's) propriety.  This sympathy with resentment against harm is the
basis for Smith's treatment of justice in TMS.

This is as much of a nutshell as I can squeeze Smith's psychology of moral
judgment into, with the caveat that it does not capture much of the nuances
(and ambiguities) of his argument.  Because the relation of sympathy and
benevolence in human nature is closely tied up with his concept of moral
sentiment, moral sentiment with the social dimension of propriety, and his
moral theory with his political economy, the range of literature can be
quite large, with different interpretations at odds with each other.

Paul Turpin